UNIVERSITY OF CINCINNATI
Date:_November 6, 2006______
I, Jennifer L. Riepenhoff______, hereby submit this work as part of the requirements for the degree of:
M.S. Chemistry in:
McMicken College of Arts and Sciences It is entitled:
The Study and Synthesis of Corannulene-based Carcerands
This work and its defense approved by:
Chair: ___ _Dr. James Mack______
___ _Dr. Dave Smithrud______
Dr. Tom Ridgway______
______
______
The Study and Synthesis of Corannulene-based Carcerands
A Thesis submitted to the
Graduate School
of the University of Cincinnati
In partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE
In the Department of Chemistry
of the McMicken College of Arts and Sciences
By
Jennifer Lynn Riepenhoff
B.S. Chemistry
University of Dayton, Ohio, May 2004
Committee Chair: Dr. James Mack
November 2006
AN ABSTRACT OF A THESIS
The Study and Synthesis of Corannulene-based Carcerands
Jennifer L. Riepenhoff
The use of nanotubes and fullerenes in various fields has been slowed due to the crude manner in which they are currently synthesized. Further, the inabilities in many cases to selectively alter these structures make it difficult to tailor these molecules for specific applications. Fullerenes have been proven useful in encapsulating atoms, however, guest entry is difficult due to its completely closed shell. Corannulene, a fullerene fragment which comprises 1/3 of fullerene[60] exhibits many of the same properties of fullerene and nanotubes and are easily modified. Our research deals with the utilization of fullerene fragments to design molecules for specific applications. Molecules using corannulene as a template will be synthesized for molecular encapsulation. The synthesis of corannulene cyclophanes attached by enediyne moieties is currently underway. It is expected that the target corannulene cyclophane will undergo Bergman cyclization to produce a molecule that can trap atoms or molecules inside.
ii iii TABLE OF CONTENTS
Chapter Page
1. Fullerenes, Nanotubes, and Corannulene……………………………………………...1
Fullerenes……………………………………………………………………...1
Nanotubes………………………………………………………………..…....6
Corannulene……………………………………………………………..…….8
2. Complexation of Corannulene and Derivatives…………………………………...…12
Endohedral Fullerenes……………………………………………………….12
Rationale and Design………………………………………………………...14
Synthesis of Carcerand………………………………………………………17
Corannulene Complexation with Hydrogen…………………………………28
Conclusions and Future Work……………………………………………….29
3. Experimental Methods……………………………………………………………….31
4. Spectra………………………………………………………………………………..39
Appendix
A. Improvements on Corannulene Synthesis…………………………………………....…..68
B. References………………...…………………………………………………………..….70
iv LIST OF FIGURES
Figure Page
Figure 1.1 – Carbon atoms in Graphite…………………………………………………….…...…1
Figure 1.2 – Carbon atoms in Diamond…………………………………………………………...2
Figure 1.3 – Fullerene[60]……………………………………………………………………..….4
Figure 1.4 – Reaction of C60 with trans-Oxiranes…………………………………………..……..5
Figure 1.5 – Nanotubes……………………………………………………………………..……..7
Figure 1.6 – Corannulene……………………………………………………………………..…...8
Figure 1.7 – Bowl Shape Structure and Electron Density of Corannulene.…………………..…..9
Figure 1.8 – Synthesis to Corannulene…………………………………………………………..10
Figure 2.1 – Endohedral Fullerene…………………………………………………………….…12
Figure 2.2 – Opening of a fullerene by organic synthesis…………………………………….…14
Figure 2.3 – Open [6,6] 1,5-corannulene cyclophane and [6,6] 1,8-corannulene cyclophane…..16
Figure 2.4 – Closed [2,2] 1,5-corannulene cyclophane and [2,2] 1,8-corannulene cyclophane…16
Figure 2.5 – [6,6] Metacyclophane synthesized by Sankararaman………………………….…..17
Figure 2.6 – Proposed Synthesis of Corannulene Cyclophanes………………………...……….18
Figure 2.7 – Friedel Crafts Acylation Reaction……………………………………….…………19
Figure 2.8 – NMR of Over Chlorination………………………...………………………………20
Figure 2.9 – Chlorination Reaction of 1,5-diacetylcorannulene…………………………..……..21
Figure 2.10 – 1H NMR of 1,5-bischlorovinylcorannulene…………………………………....…21
Figure 2.11 – Chromatogram of Separation of Coupling Reaction…………………………..….23
Figure 2.12 – 1H NMR of Peak 1…………………………………………………………...……24
v
Figure 2.13 –1,8 bis-chloroenynecorannulene (25)………………………………………...……25
Figure 2.14 – 1H NMR of 1,8 bis-chloroenynecorannulene (25)………………………..………26
Figure 2.15– 13C NMR of 1,8 bis-chloroenynecorannulene (25)………………….…………….26
Figure 2.16 – Electrospray MS of 1,8 bis-chloroenynecorannulene with AgBF3 (25)…………..27
Figure 2.17 – Ammonium Ion encapsulated inside the closed [6,6] 1,5-corannulene
cyclophane……………………………………………………………………………….30
Figure 4.1 – 1H NMR of 2,7-bis(diethylcarbamoyloxy)naphthalene (2)………………..………39
Figure 4.2 – 13C NMR of 2,7-bis(diethylcarbamoyloxy)naphthalene (2)……………………….40
Figure 4.3 – 1H NMR of 2,7-dimethylnaphthalene (3)…………………………………………..41
Figure 4.4 – 13C NMR of 2,7-dimethylnaphthalene (3)………………………………….…..…..42
Figure 4.5 – 1H NMR of 3,8-dimethylacenaphthenequinone (4)…………………………..…….43
Figure 4.6 – 1H NMR of 3,8-dimethylacenapthenequinone (4) using high dilution…………….44
Figure 4.7 – 13C NMR of 3,8-dimethylacenaphthenequinone (4)………………………….……45
Figure 4.8 – 1H NMR of 1,6,7,10-tetramethylfluoranthene (5)…………………………….……46
Figure 4.9 - 13C NMR of 1,6,7,10-tetramethylfluoranthene (5)………………………………….47
Figure 4.10 – 1H NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)………...…….…..48
Figure 4.11 – 13C NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)………….………49
Figure 4.12 – 1H NMR of 1,2,5,6-tetrabromocorannulene (7)……………………………….….50
Figure 4.13 – 1H NMR of Corannulene (8).………………………………………………..……51
Figure 4.14 –13C NMR of Corannulene (8)…………………………………………..….………52
Figure 4.15 – 1H NMR of 1,5-diacetylcorannulene (9)……………………………..……….…..53
Figure 4.16 – 13C NMR of 1,5-diacetylcorannulene (9)…………………………………………54
vi Figure 4.17 – 1H NMR of 1,8-diacetylcorannulene (10)…………………………………….…..55
Figure 4.18 – 13C NMR of 1,8-diacetylcorannulene (10)…………………………………….….56
Figure 4.19 – 1H NMR of 1,5-bischlorovinylcorannulene (11)………………..…………...……57
Figure 4.20 – 13C NMR of 1,5-bischlorovinylcorannulene (11)………………..………………..58
Figure 4.21 – 1H NMR of 1,8-bischlorovinylcorannulene (12)………………………………….59
Figure 4.22 – 13C NMR of 1,8-bischlorovinylcorannulene (12)…………………………………60
Figure 4.23 – 1H NMR of 1,5-dialkynecorannulene (13)………………………………….…….61
Figure 4.24 – 13C NMR of 1,5-dialkynecorannulene (13)……………………………….………62
Figure 4.25 – 1H NMR of 1,8-dialkynecorannulene (14)………………………………………..63
Figure 4.26 – 13C NMR of 1,8-dialkynecorannulene (14)……………………………………….64
Figure 4.27 – 1H NMR of 1,8 bis-chloroenynecorannulene (25)………………………………..65
Figure 4.28 – 13C NMR of 1,8 bis-chloroenynecorannulene (25)…………………….…………66
Figure 4.29 – Electrospray MS of 1,8 bis-chloroenynecorannulene with AgBF3 (25)…………..67
vii CHAPTER 1
FULLERENES, NANOTUBES, AND CORANNULENE
Fullerenes
Carbon, the sixth most abundant element, is widely distributed in nature and an essential
element for humans. Carbon is a base for coal, oil, sugars, proteins, and all known living
organisms. Besides being bonded to other atoms, carbon can form stable bonds with itself to
form all carbon molecules such as graphite and diamond. Based on hybridization and
arrangement of the atoms, these molecules will have vastly different properties
Figure 1.1 – Carbon atoms in graphite
The carbon atoms in graphite (Figure 1.1) are all sp2-hybridized and possess bond lengths of 1.42 Å with bond angles of 120 degrees. Every carbon is bonded to three other neighboring
1 carbons in a plane. The π-orbitals all lie parallel to one another and are perpendicular to the graphitic plane, generating electron density above and below the plane. Each carbon atom contributes one electron which is allowed to move freely throughout the carbon network. For this reason, graphite can be used to conduct electricity and heat along the planes of carbon layers.
Unlike graphite, all of the carbon atoms in diamond (Figure 1.2) are sp3 hybridized with each atom being surrounded by four other carbons, forming a three dimensional network.
Figure 1.2 – Carbon atoms in diamond
Each C-C bond length is 1.54 Å and the atoms are arranged tetrahedrally with a C-C-C bond angle of 109.5 degrees. Diamond has a dense, extremely stable structure and conducts heat well, but not electricity. This is due to the bonding electrons being localized in the carbon atoms so there is no movement of electrons.
2 Until the late twentieth century, graphite and diamond were the only known forms of
molecular carbon; since then two new forms of molecular carbon were discovered, namely
fullerenes and nanotubes. Each of these molecules has become very useful to scientists because
of their unique electronic structural and chemical properties.1 These molecules are the only
forms of molecular carbon that can be chemically altered.
Robert Curl, Harold Kroto, and Richard Smalley discovered fullerenes in 1985 by using
laser vaporation of graphite, in which a laser beam strikes a graphite disk, producing a plasma of
vaporized carbon atoms. Time-of-flight mass spectrometry found soot containing of only carbon
clusters and the distribution of cluster sizes depended dramatically on the experimental conditions. Even numbered clusters with 38-120 carbon atoms resulted, with the most abundant being a sixty carbon allotrope. After further examination, they determined that this was a stable form of carbon in which 60 carbon atoms were arranged in a cage. They later named their discovery buckminsterfullerene because of the similarity to the geodesic domes developed by architect Buckminster Fuller; this discovery earned them the Noble Prize in 1996.
Fullerenes are molecules entirely composed of carbon that are spherical in shape. The most common fullerene is C60 (Figure 1.3), a truncated icosahedron that looks like a soccer ball
with 12 pentagons and 20 hexagons. The five-membered rings provide the curvature and are
governed by the isolated pentagon rule, a rule that states in the most stabile form of a fullerene no two five-membered rings can be adjacent to one another.
3
Figure 1.3 – Fullerene[60]
C-C bonds at 6-5 junctions (i.e., junctions where a six membered ring is adjacent to a five membered ring) measure 1.45 Å. while C-C bonds at 6-6 junctions (i.e., junctions where two six- membered rings are adjacent) measure 1.40 Å.2 The average inner diameter of fullerene [60] is
about 7 Å and the outer diameter is about 10 Å. The bowl shape at each sp2 center introduces
some strain into the molecule, but the high symmetry distributes the strain evenly across the
entire structure. Synthesizing fullerenes by laser evaporation of graphite only produced
milligram quantities of fullerene[60], thus there was a need for bulk production in order to
further study fullerenes and their properties. In 1990, Kratschmer and Huffman developed a way
to synthesize gram quantities of fullerenes.3 This method in which a current is passed between
two graphite electrodes in an atmosphere of helium causes the graphite to vaporize, producing
several grams of soot that is comprised between 7-10% of fullerenes. Since this breakthrough,
many scientists have been able to study the chemistry of fullerenes and have made many
fullerene derivatives.
Fullerenes react as electron poor species, readily undergoing nucleophilic addition, and
acts as a dienophile in cycloaddition chemistry. The 1,3-dipolar cycloaddition reaction is one of
4 the more common reactions for the functionalization of fullerenes. Different 1,3-dipoles such as
azomethine ylides, diazo compounds, and nitrile oxides have been reported to react with
4 fullerene C60. Epoxides are known to undergo thermal or photochemical 1,3-dipolar
cycloaddition via carbonyl ylides with alkenes5 and alkynes6. Wang and co-workers investigated
7 the reaction of C60 with epoxides. They showed that whether the reagents were cis or trans
oxiranes, cis products were always exclusive or predominantly seen.
Figure 1.4 – Reaction of C60 with trans-Oxiranes
Fullerenes have potential use in various applications such as drug delivery, information
technology, and non-linear optics. Since fullerenes has a small size, spherical shape, and hollow
interior, it shows promise for certain types of drug design, which can be used for treating
diseases including HIV and cancer.8 Immense efforts have been made in the design of organic systems with nonlinear optical properties such as polymers or those that have an extended π- conjugated electron system. Optical applications need the linear absorption of a molecule to be near the IR region. Fullerenes have been looked at extensively because of the π-electrons delocalized along the structure. Their absorption is strong in the UV region and a weak absorption in the visible range. This may be promising for fullerene derivatives or any other π- conjugated system to push it farther down to the IR region.
5 Nanotubes
Nanotubes were originally discovered in 1991 by Sumio Iijima as a spin off of
fullerenes.9 They are made in a similar fashion as fullerenes by using the Kratschmer and
Huffman arc vaporization method. By changing the current from alternating to direct current,
nanotubes were found on the carbon electrodes. The first form of nanotubes discovered were
multi-walled tubes (i.e. tubes contained inside other tubes). While shortly after, upon slightly
changing conditions, single walled nanotubes were synthesized. Single walled nanotubes (i.e.
nanotubes that are one atom thick) are synthesized by passing a carbon-containing gas, such as a
hydrocarbon, over a catalyst containing Fe, Co, or Ni. The particles catalyze the breakdown of the gaseous molecule into carbon and a tube begins to grow at the metal at the tip. By changing the catalyst and growth conditions, single walled nanotubes have been made with a diameter ranging from 7 – 16 Å. Since the growth mechanism of these nanotubes is not very well
understood, it limits the production of size specific nanotubes. Impurities are a problem in both
synthetic methods and are hard to remove, lowering their mechanical properties. In addition to the problem of synthesizing specific size tubes, nanotubes can be twisted along its backbone in an infinite number of twist angles, whereby each twist angle represents a different tube possessing different properties.
6
Figure 1.5 – Nanotubes
Nanotubes are about 10,000 times thinner than a strand of human hair and depending on their
form, measuring from a few nanometers in diameter and several microns in length. Carbon
nanotubes have high flexibility, unlike carbon fibers. Nanotubes can be semi-conducting or
metallic depending on their helicity and diameter. Nanotubes can be easily doped and can
potentially replace metals as the primary conductant used in circuits. Metallic nanotubes can
possess conductivity higher than copper, which show great electronic promise. All nanotubes
are likely to be good thermal conductors along the tube, exhibiting a property known as ballistic
conditions. This is where electrons can flow through a material without collisions. Their ability
to store electric charge is expected to aid in the development of sensors needed in medical and
homeland security applications. In order to make devices out of nanotubes, they have to be
manipulated in a certain way such as the shape, orientation, and position. Currently, there is no
reliable way to develop and arrange nanotubes in this manner. Scientists have been unable to
control the types of nanotubes produced and used for various applications. In order for nanotubes to become a feasible material, a solution is needed to control their production.
7 Corannulene
Corannulene (Figure 1.6), 1/3 that of fullerene[60], consists of a cyclopentane ring fused
with 5 benzene rings with a molecular formula of C20H10.
Figure 1.6 – Corannulene
Corannulene is bowl shaped and has an inversion barrier of about 10 kcal/mol.10 Due to this
bowl shape and connection to fullerene, it is also known as a buckybowl. It has a bowl depth of
0.87 Å, with a dipole moment of 2.07 D.11 The electron density of corannulene is centered on the 5-membered ring with the potential to serve as hosts for various electron deficient guests.
8
Figure 1.7 – Bowl shaped structure and Electron Density of Corannulene. Red indicates high levels of electron density. Blue indicates low levels of electron density.
Since corannulene is not readily available, it has to be independently synthesized. Barth and Lawton first prepared corannulene in 1965 but the synthesis was long, containing 17 steps, and only produced small quantities of corannulene.12 Therefore, the chemistry and properties of corannulene were not fully understood due to the difficulty of the synthesis. It wasn’t until 1991 when the Scott group published a new synthetic route that used flash vacuum pyrolysis (FVP) to obtain corannulene so further studies could be done.13 Over the years, improvements on this synthesis have been prepared such as eliminating steps to obtain corannulene.14 Our most recent synthesis is outlined in Figure 1.8.
9 O
N Cl HO OH N O O N
O O pyridine 1 2
O O NiCl2(dppp) MeMgBr-Et2O Cl Cl
AlBr3 3
O O 1. O KOH, MeOH
2. Ac2O 4 5
Br Br
Br Br NBS, CCl4 NaOH, dioxane Br Br H O light Br Br 2
6
Br Br
Zn dust, KI Br Br HCl
7 Corannulene 8
Figure 1.8 – Synthesis to Corannulene
10 The lowest unoccupied molecular orbitals of corannulene are low lying and doubly degenerate, which signifies that the reduced states of corannulene could be possibly stable even in a highly anionized state. This is similar to C60 which has a 3 fold degenerate LUMO and can
accept up to 6 extra electrons to form higher anions. Because of corannulene’s low-lying
LUMO, it can accept up to four extra electrons.15 It is reduced both electrochemically and by
alkali metals such as lithium and potassium. It can be reduced up to 4 times, giving a radical
anion, dianion, trianion and tetraanion, which have all been examined.16 Once corannulene is
reduced four times, it has been shown to become two tightly complexed dimers. The four lithium atoms are held tightly between the two hydrocarbon tetraanions.17 The tetraanion can be
thought of as an “annulene within an annulene”. This has been reported previously, but only
with monolithium derivatives of cyclohexenyl or cyclopentadienyl systems. Due to the limited
availability of corannulene many of its properties are still unknown. The focus of our research is
to unlock the secrets possessed by this molecule.
11 CHAPTER 2
COMPLEXATION OF CORANNULENE AND DERIVATIVES
Endohedral Fullerenes
Endohedral fullerenes, molecules encapsulated inside a fullerene, enhance certain
properties of fullerenes (Figure 2.1).
Figure 2.1 – Endohedral Fullerene
Their cage-like structure can hold a variety of metal atoms and small molecules inside.
Endohedral fullerenes are important for various applications ranging from molecular electronics to the study of reactive intermediates.18 Because of their electronic properties, fullerenes have
been studied for data storage devices and solar cells. Solar cells made out of organic molecules
are better because they are more flexible than silicon and are lighter in weight. MRI contrast
agents enhance the quality of the images, which will help in the detection of abnormalities in the human body. Endohedral fullerenes may be useful for bringing metal contrast agents into the body for MRI scans without harming the patient’s body. Gadolinium is already being used as a contrast agent and fullerenes might improve this process by being able to entrap the molecule
12 inside longer so full analysis can be done.19 Fullerenes can also be used for NMR analysis by
trapping intermediates inside while running a sample. Endohedral fullerenes have more
enhanced optical properties than their empty fullerene counterpart. The caged atom can
contribute electrons to the fullerene molecules, which changes the electronic and magnetic
properties. Metal-to-cage transfer appears to be a common feature of metal encapsulated
endohedral fullerenes. They are important because the metal inside becomes a stable ion pair so
the endohedral cations should have a highly charged anionic carbon cage for charge compensation. This gives the endohedral fullerenes delocalized charge-transfer states, which are important for non-linear optics. Another useful application of endohedral fullerenes is that it can capture reactive intermediates and stabilize reactive species inside the cage. Successful attempts have been encapsulating benzyne,20 cyclobutadiene,21 and a nitrogen atom without being bonded
to the fullerene surface.22 Hirsch showed that fullerene[60] can encapsulate and stabilize a
single nitrogen atom inside its cavity.23
Successful efforts at endohedral fullerenes have been reported, however, there are many
problems that come with them. Guest entry into fullerenes is difficult due to its closed shell.
The size of the molecule is limited because it has to be force-fed into the fullerene with high
pressures and temperatures to encapsulate the molecule. Saunders and co-workers use a high-
pressure vessel with a copper ampule to encapsulate molecules.24 The copper ampule holds the
fullerene and noble gas, which is then put into the chamber of the vessel. This chamber is filled
with water and heated to 650°C and a pressure of 3,000 atm. At this temperature, the copper
collapses and the fullerene bonds are broken so the noble gas can get inside. Although this
method is successful, only 1 in 1000 fullerenes become endohedral, which is less than a 1%
yield. Other research attempts have been to break the C-C by synthesizing the fullerene.
13 Komatsu and co-workers have shown this route by opening the fullerene ring.25 A 7-step
synthesis is performed on the fullerene in order to open the carbon framework, insert the hydrogen gas, and close it by organic synthesis.
Figure 2.2 – Opening of a fullerene by organic synthesis
Opening and closing of the fullerene requires high temperatures, but once a gas is encapsulated, low temperatures are necessary so it does not escape in the reformation of the ring. Because of this complexity, results have only proven small yields of an encapsulated fullerene. The encapsulation of hydrogen is maintained under normal conditions and can be released by heating at temperatures higher than 160°C. Komatsu and co-worker also had problems opening a hole on only one side of the fullerene making the overall process very none selective.
Rationale and Design
In order to eliminate many of the problems of using fullerenes as hosts, corannulene
derivatives can be tailored to complete this task. Corannulene provides an open concave carbon
surface for binding and the rim carbon atoms capped by hydrogen atoms available for
14 coordination. The accessibility of the concave and convex faces of corannulene may allow both
endo and exo metal complexation. Siegal and co-workers were the first to bind metal ions to
corannulene in solution and isolate a stable complex.26 Corannulene has several potential sites
for protonation such as binding to one carbon, across the C-C bond, or positioning itself over the
ring giving a σ-complex or a π-face complex.27 The most preferred are the σ-complexes.
Protonation at the outermost carbon is less favorable, and protonation at the intermediate carbon
is significantly lower than that at the hub carbon. Seiders and co-workers also investigated how
protonation affects the barrier for bowl-to-bowl inversion of corannulene.28 They showed that
bulky substituents placed in the peri positions causes a flattening of the corannulene bowl and a
decrease of the barrier. Dunbar showed that alkali metals Li+, Na+, and K+ and transition metal
ions Ti+, Cr+, Ni+, and Cu+ also bind to corannulene with calculated binding energies ranging
anywhere from 20-50 kcal/mol.29 For the alkali metals, binding to the outside convex face is
preferred, and for the transition metals a much larger preference for the outside face is found.
There is a steady decrease in binding energies going from Li+, Na+, and K+, reflecting on the
increasing size of the ions and polarization binding energy.
We have targeted two corannulene-based cyclophanes to examine their ability to
encapsulate atoms and small molecules. The [6,6] 1,5-corannulene cyclophane (23) and the [6,6]
1,8-corannulene cyclophane (24) (Figure 2.3). Each cyclophane is held together by an enediyne moiety that can undergo Bergman cyclization30 to convert these molecules to carcerands. The
two different sized carcerands will allow us to encapsulate different sized guests. Corannulene
has already demonstrated the ability to form strong complexes with metals and other guests. 31
15
10.8 Å
7.2 Å 10.5 Å
23 24
Figure 2.3 – Open [6,6] 1,5-corannulene cyclophane and [6,6] 1,8-corannulene cyclophane
The main difference between the 1,5 and 1,8-corannulene cyclophane is the distance of the cavity between the two moieties. According to B3LYP-6-31G* calculations32, the Bergman cyclization is calculated to shorten the distances in the 1,5-corannulene cyclophane from 7.2 Å to
5.4 Å and the 1,8-corannulene cyclophane from 10.5 Å to 5.9 Å (Figure 2.4). The Bergman cyclization is triggered when the distance between the two terminal alkyne carbons is in the range of 2.9-3.5 Å. It is already known that a metal complexation can undergo this change to bring on the Bergman cyclization at ambient temperature.33
5.4 Å 5.9 Å
25 26
Figure 2.4 – Closed [2,2] 1,5-corannulene cyclophane and [2,2] 1,8-corannulene cyclophane
16 Synthesis of Carcerand
Sankararaman and co-workers have recently synthesized a [6,6] metacyclophane (Figure
2.5) with enediyne bridges starting with 1,3-diethynylbenzene.34 We followed a similar synthetic pathway to synthesize the desired corannulene cyclophanes.
Figure 2.5 – [6,6] Metacyclophane synthesized by Sankararaman
Friedel-Crafts acylation of corannulene has been shown to give two isomers, 1,5- diacetylcorannulene and 1,8-diacetylcorannulene. These isomers are able to be separated and will be carried through the synthesis independently to give the two cyclophanes shown previously.
17 O O O Cl Cl O P Cl Cl O Cl Cl LDA
AlCl3 DCE THF
8 10 12
O O O
1)EtMgBr,THF 2) DMF p-TSOH Ethylene Glycol
14 16 18
O FeCl . 6H O Pd(PPh3)4, CuI, n-BuNH2, 3 2 O O Cl Cl O
20
O TiCl3, Zn-Cu O DME
22 24
Figure 2.6 – Proposed Synthesis of Corannulene Cyclophanes
18 Friedel-Crafts acylation was accomplished and two isomers were obtained as shown in
Figure 2.7.
O O O O
Cl + O AlCl3
8910
27% 45%
Figure 2.7 – Friedel Crafts Acylation Reaction.
Separation of 1,5-diacetylcorannulene (9) and 1,8-diacetylcorannulene (10) was achieved by column chromatography using pure CH2Cl2 and switching to 99:1 CH2Cl2:EtOAc to give us a
72% yield with a ratio of 1:1.6, respectively. Next, bischlorovinyl corannulene was attempted using PCl5 in refluxing toluene on 1,8-diacetylcorannulene. NMR results were inconclusive, showing two sets of resonances around 4 and 1.5 ppm (Figure 2.8).
19
Figure 2.8 – NMR of Over Chlorination
As a test reaction we used acetophenone in refluxing toluene with PCl5 to get chlorovinyl
benzene. We were unable generate chlorovinyl benzene possibly due to over chlorination. We switched to the use of 1,2 phenylene phosphorotrichloridite as the chlorination agents. After
demonstrating success with acetophenone, we attempted the process with 1,8-
diacetylcorannulene. We were able to obtain the desired product of 1,8-bischlorovinyl
corannulene (12) in 91% yield. Next, using 1,5-diacetylcorannulene, chlorination was also successful by giving product (11) and NMR gave the desired doublet at 5.8 ppm for the alkene hydrogens.
20 O
O Cl Cl P Cl O Cl Cl
O DCE
9 11
92%
Figure 2.9 – Chlorination Reaction of 1,5-diacetylcorannulene
Cl Cl
11
Figure 2.10 – 1H NMR of 1,5-bischlorovinylcorannulene
Next, elimination was carried out using LDA purchased from Acros. After standard work up procedures, the NMR showed peaks in the aromatic region farther upfield from corannulene and were undeterminable. Further analysis from GC and separate water washes on
21 the LDA itself concluded that the material contained ethylbenzene. This impurity could not be
separated from our own terminal alkynes, so it was decided LDA would be made from n-BuLi
and diisopropylamine. This was successful for both 1,5-dichlorovinylcorannulene and 1,8-
dichlorovinylcorannulene using dry THF. NaH was attempted to see if yields could be improved
but starting material was recovered. BuLi was also tried, but reduced the corannulene ring.
The next reaction was to formylate one side of the terminal alkynes in order to protect it
while Sonogashira coupling could be done on the other terminal alkyne. Various methods to
protect only one alkyne were troublesome. Test reactions were done on 1,3-diethynylbenzene to
optimize the conditions needed for this reaction. After unsuccessful attempts using LDA as the
base, ethylmagnesium bromide was attempted. Taking the proton was a success with this base, but yields no more than 20% were recovered. Since formylating one side was unsuccessful, more test reactions were done to see if protecting one side was needed at all. Sonogashira
coupling was done on 1,3-diethynylbenzene using cis-dichloroethene to see if we could reproduce the procedures performed previously by Sankararaman in better yields. They report
2% yield coupling on both sides to get the product shown in Figure 2.5. Conditions were tested
using Pd(PPh3)4 and Pd(PPh3)2Cl2 as different catalysts, Et3N and n-BuNH2 as bases, slow
addition, and using a co-solvent such as THF. The best conditions for this reaction was using
Pd(PPh3)2Cl2 as the catalyst, n-BuNH2 as the base, and adding 1,3-diethynylbenzene dropwise
using a syringe pump at 2mL/hr. This reaction was repeated on 1,8-dialkynyl-corannulene to see
if we could generate our final product of [6,6] 1,8-corannulene cyclophane (24). The reaction
was stirred overnight. Separation of the crude product gave 4 peaks.
22
Figure 2.11 – Chromatogram for Separation of Coupling Reaction
23 After full analysis of NMR and mass spectroscopy we have only been able to fully characterize one structure. Peak1 has the appearance of the desired cyclophane by 1H NMR but due to very little material, 13C NMR could not be determined. Further, MS was not able to confirm the desired product.
Figure 2.12 – 1H NMR of Peak 1
Further analysis of peak 2 showed it to be 1,8 bis-chloroenynecorannulene (Figure 2.13).
24 Cl Cl
Figure 2.13 – 1,8 bis-chloroenynecorannulene (25)
This was determined by 1H NMR by giving two doublets at 6.25 and 6.57 ppm, which are the alkene hydrogens. There is no singlet for the terminal alkyne at 3.4, proving the reaction did couple together. The corannulene peaks are still shown at 7.768, 7.776, 8.03, and 8.188 ppm.
13C NMR confirmed this by showing 15 carbons due to the plane of symmetry. Electrospray-
MS showed this product coupled to Ag+ by giving a mass of 526 and coupled to itself with an
Ag+ ion in the middle with a mass of 944.
25 Cl Cl
Figure 2.14 – 1H NMR of 1,8 bis-chloroenynecorannulene (25)
Cl Cl
Figure 2.15 – 13C NMR of 1,8 bis-chloroenynecorannulene (25)
26
Figure 2.16 – Electrospray MS of 1,8 bis-chloroenynecorannulene with AgBF3 (25)
Peak 3 and 4 are believed to be some form of polymer but further analysis is needed.
27 Corannulene Complexation with Hydrogen
Hydrogen and fuel cell technologies have potential in the future to solve some of the
major energy and environmental problems we are having today. In order to have hydrogen
powered vehicles, there needs to be a way to store hydrogen and there has to be enough of it to
allow for the same driving distance as today’s cars. The US DOE has determined that an energy
density of 6.5-weight percent hydrogen must be achieved, in order for a hydrogen storage system
of appropriate weight and size to facilitate a fuel cell vehicle driving distance of 560
kilometers.35 The popular storage methods currently are liquid hydrogen and compressed
hydrogen but they require that the fuel be kept at extremely low temperatures or high pressures.
Hydrogen can also be stored on the surface of solids or within solids. By using solids, this may
make it possible to store larger quantities of hydrogen in smaller volumes at lower pressure and
room temperature. Carbon nanotubes and fullerenes have been viewed as a potential for
hydrogen storage for many years but lack of practical storage methods have forced scientists to
look elsewhere. Dillon suggested that values of ~5-10 wt % hydrogen using nanotubes are
obtainable, although this is still being investigated.36 Since corannulene is a fragment of a
fullerene[60], it has been looked at intensely for storage. The bowl-shaped figure of corannulene
suggests that this curved structure can increase the adsorption energy of hydrogen. Studies have been done using molecular dynamics, ab initio calculations, and experimental determinations to see how well corannulene can absorb hydrogen.37 In the molecular dynamics calculations, the
weight percent of hydrogen at 300 K is 2 wt %, and at 139 bar, it increases to 3.89 wt %.
Experimental procedures were conducted under temperatures of 297 K and pressure of 100 bar,
which are compatible for future applications such as hybrid vehicles. Studies were also done to
28 investigate how many hydrogen molecules can be accommodated on the surface of a
corannulene ring, if the electron density above/below the ring acts independently, and if the
binding energy of hydrogen molecules sandwiched between two corannulene rings is doubled.
The binding energy per hydrogen molecule is about double what it is when there is only one
corannulene ring interacting with a hydrogen molecule. Experimental and calculated results
agree with one another and their adsorptive properties are greatly enhanced. These studies show
great promise for using corannulene as an alternative to hydrogen storage.
Conclusions and Future Work
We have demonstrated the use of corannulene in potential applications. Once more 1,8- dialkynecorannulene is made, it can be coupled to the chlorinated alkene product shown in
Figure 2.6 to get the desired compound [6,6] 1,8-corannulene cyclophane (24). Sonogashira coupling can also be tried on the 1,5-dialkynecorannulene to see if the reaction proceeds the same or if we can get more of our desired product.
Once the synthesis is carried out again and more product can be achieved, we will obtain an X-ray crystal structure of each cyclophane. Differential Scanning Calorimetry will be done to determine the energy required to undergo a Bergman cyclization of the enediyne bridges. Once this cyclization is complete, we will obtain x-ray structures of [2,2] 1,5-corannulene cyclophane and [2,2] 1,8-corannulene cyclophane with and without molecules encapsulated inside. Studies can also be done such as solution phase NMR and X-ray crystallography to determine the complexation with various host guests.
29 Molecules of interest for encapsulation are neutral molecules such as water, carbon
dioxide, and nitrogen gas. We will also study the encapsulation of cationic ions such as Na+, K+, and ammonium ion shown in Figure 6 and anionic species such as hydroxide and formate. Once we have successfully encapsulated these guests, studies may be extended to several other guests of each type.
1,4 cyclohexadiene
CDCl3
Figure 2.17 – Ammonium Ion encapsulated inside the closed [6,6] 1,5-corannulene cyclophane.
30 CHAPTER 3
EXPERIMENTAL METHODS
Instrumentation and Materials
Diethyl ether, Tetrahydrofuran, and Dichloroethane were purified from an MBraun
solvent purification system. All column separations were done on a Combiflash Companion
Instrument by Teledyne Isco using 4, 12, and 40g silica columns. Aldrich provided
diisopropylamine, n-butyl lithium (1.6M in hexanes), Methylmagnesium Bromide (3M in ether),
AlCl3 (99%), and AlBr3 (98%). Strem provided NiCl2(dppp). Throughout the experimental, the
following abbreviations are used: diethyl ether (Et2O), n-butyllithium (n-BuLi), ethyl acetate
(EtOAc), dichloromethane (CH2Cl2), tetrahydrofuran (THF), 1,2-dichloroethane (DCE).
Synthesis of 2,7-bis(diethylcarbamoyloxy)naphthalene (2)
Modified procedures as prepared by the published method.38 Into a 1-L round-bottom
flask, 2,7-dihydroxynaphthalene (49.7g, 0.310 mol), pyridine (700mL) and diethylcarbamoyl
chloride (120 mL) is added and refluxed overnight. The solution is then poured into a 2-L
Erlenmeyer flask containing a solution of hydrochloric acid (6M, 600mL). A light brown solid,
which solidified out of solution, was filtered using a Buchner funnel, washed with water and
dried overnight. The resultant product is a light brown solid (110.86g, 99.7%). 1H NMR (400
MHz, CDCl3) δ 7.794 (d, 1H, J = 8.8 Hz), 7.515 (s, 1H), 7.239 (d, 1H, J = 8.8 Hz), 3.429 (q, 4H,
13 J = 6.4 Hz), 1.238 (t, 6H, J = 6.4 Hz). C NMR (400 MHz, CDCl3) δ 154.063, 149.607,
134.301, 128.749, 128.650, 120.996, 117.905, 42.131, 41.811, 14.152, 13.281.
31 Synthesis of 2,7-dimethylnaphthalene (3)
Modified procedures as prepared by the published method.38 An oven-dried 2-L round-
bottom flask is equipped with a reflux condenser and an oven-dried dropping funnel. Under a
flow of nitrogen, the flask is charged with 2,7-bis(diethylcarbamoyloxy)naphthalene (90.42g,
0.253 mol), the catalyst NiCl2 (2.44g), and anhydrous diethyl ether (700mL). A red mixture is
obtained. The dropping funnel is charged with methylmagnesium bromide (3M in diethyl ether,
350mL), which is added dropwise. The mixture is stirred at 40°C for 48 hours. The dropping
funnel is charged with hydrochloric acid (6M, 400mL) and slowly added to the reaction over 30
minutes in order to maintain a gentle reflux. The aqueous layer is separated and extracted further
with diethyl ether. The combined organic layers are washed with water and dried over
magnesium sulfate. After filtration and evaporation of the solvent, the compound is dried under
vacuum to a constant weight to afford a beige solid (38.95g, 98.85%). 1H NMR (400 MHz,
13 CDCl3) δ 7.668 (d, 1H, J = 8.4 Hz), 7.489 (s, 1H), 7.212 (d, 1H, J = 8.4 Hz), 2.471 (s, 3H). C
NMR (400 MHz, CDCl3) δ 135.388, 133.855, 129.899, 127.364, 127.190, 126.192, 21.707.
Synthesis of 3,8-dimethylacenaphthenequinone (4)
39 Procedures followed as prepared in the published method. CH2Cl2 (500mL) is put into
an oven-dried round-bottom flask and aluminum bromide (117.88g, 0.442 mol) is added while
under nitrogen and cooled using an ethylene glycol dry ice bath. A solution of 2,7- dimethylnaphthalene (36.86g, .236 mol) and oxalyl chloride (19.27mL, 0.221mol) diluted with
CH2Cl2 (100mL) is added dropwise over 1 hour. The solution is then carefully quenched by
pouring into ice water. The organic layer is then washed with water, dried over magnesium
sulfate, filtered and evaporated onto silica gel. The solution is then passed through a silica plug
32 using 1:1 CH2Cl2/hexanes to get rid of the fast moving impurity switching between 2:1
CH2Cl2/hexanes and finally to pure CH2Cl2. Fractions are collected in 500mL portions and
evaporation yields a golden yellow solid (21g, 42.3%) as a mixture of 3,8-
dimethylacenaphthenequinone and 4,7-dimethylacenaphthenequinone. 1H NMR (400 MHz,
CDCl3) δ 8.013 (d, 1H, J = 8.4 Hz), 7.932 (s, 1H), 7.844 (s, 1H), 7.481 (d, 1H, J = 8.4 Hz), 2.854
13 (s, 3H) 2.672 (s, 3H). C NMR (400 MHz, CDCl3) δ 188.617, 188.142, 146.883, 143.007,
142.982, 138.933, 137.422, 131.659, 131.048, 130.699, 130.546, 128.067, 127.331, 124.120,
122.371, 22.370, 18.020.
Synthesis of 1,6,7,10-tetramethylfluoranthene (5)
Procedures followed as prepared in the published method.40 A 20% solution of
potassium hydroxide in methanol (100mL) is added to a solution of 3,8-
dimethylacenaphthenequinone (10.39g, 0.0495 mol) and 3-pentanone (25mL) in methanol
(50mL). The solution is stirred at room temperature for 1 h, diluted with water (250mL) and
extracted with CH2Cl2. The organic layer is washed with 10% aqueous hydrochloric acid
(100mL), dried with magnesium sulfate, filtered and evaporated. The crude oil is then transferred to a 350 mL sealable reaction vessel and 2,5-norbornadiene (30mL) and acetic anhydride (100mL) is added. The vessel is sealed and placed in an oil bath at 130°C for 72
hours. The reaction then is cooled to ambient temperature and neutralized with 10% aqueous
sodium hydroxide (100mL), and extracted 3 times with water and CH2Cl2. The organic layer is
dried over magnesium sulfate, filtered, and evaporated to yield a dark brown oil. The oil is
purified using a silica plug with cyclohexane as the solvent. The product is a golden yellow oil
1 that solidifies upon standing (7.18g, 56.67%). H NMR (400 MHz, CDCl3) δ 7.689 (s, 1H),
33 7.597 (d, 1H, J = 8 Hz), 7.432 (s, 1H), 7.274 (d, 1H, J = 8 Hz), 7.043 (s, 1H), 7.002 (s, 1H),
13 2.768 (s, 3H), 2.685 (s, 3H), 2.569 (s, 3H). C NMR (400 MHz, CDCl3) δ 139.882, 137.485,
134.853, 133.661, 131.912, 131.784, 131.662, 130.636, 129.722, 129.565, 129.418, 126.583,
126.105, 124.560, 124.272, 25.094, 24.283, 22.642, 20.328.
Synthesis of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)
Modified procedures as prepared by the published method.40 1,6,7,10-
tetramethylfluoranthene (4.93g, 0.0191 mol), N-bromosuccinimide (33.99g, 0.191 mol), and
benzoyl peroxide (20mg) in carbon tetrachloride (250mL) is irradiated with incandescent light
(150 W) and refluxed for 3 days. The solvent is distilled off and the solid dissolved in CH2Cl2
(200mL), washed 2 times with water (100mL), dried over magnesium sulfate, filtered and
1 evaporated to yield a golden solid (16.1g, 94.7%). H NMR (400 MHz, CDCl3) δ 8.257 (d, 1H, J
= 13.6 Hz), 8.188 (s, 1H), 7.969 (d, 1H, J = 13.6 Hz), 7. 192 (s, 1H), 7.070 (s, 1H). 13C NMR
(400MHz, CDCl3) δ 137.959, 136.559, 132.373, 131.867, 131.596, 130.154, 130.063, 129.173,
127.691, 38.980, 38.369, 29.538, 28.677.
Synthesis of 1,2,5,6-tetrabromocorannulene (7)
Modified procedures as prepared by the published method.41 Sodium hydroxide (9g)
pellets and water are put into a 500mL round-bottom flask. Octabromide (18.81g, 0.0211 mol)
and 1,4-dioxane (250mL) are added dropwise to the mixture while refluxing for 2 hours. The
solution is then washed with hydrochloric acid (6M, 500mL) and settled for 20 minutes. The
solution is then filtered with a büchner funnel to give a dark orange solid (8.19g, 68.45%).
34 Synthesis of Corannulene (8)
Modified procedures as prepared by the published method.41 25 mL of 10% aqueous
hydrochloric acid is added to a suspension of tetrabromocorannulene (6.04g, 0.0106 mol), 72g
zinc dust, and 25.8g KI in 250mL of ethanol, and the reaction mixture is refluxed for one day.
The zinc is filtered off using a Büchner funnel and the resulting yellow filtrate is evaporated to a small liquid. CH2Cl2 is added and extracted with water, and the organic layer is then dried over
magnesium sulfate, and evaporated to yield a golden solid. The product was dried onto silica and separated with an automated column using 100% cyclohexane to yield a pale yellow solid
1 13 (1.51g, 56.6%). H NMR (400 MHz, CDCl3) δ 7.763 (s, 1H). C NMR (400 MHz, CDCl3)
δ 135.835, 130.883, 127.062.
Synthesis of Diacetylcorannulene (9 and 10)
To a solution of dry CH2Cl2 (25mL) and aluminum chloride (3.47g, 0.026 mol) in an
oven-dried round-bottom flask is added acetyl chloride (3.71mL, 0.052 mol) under nitrogen and
stirred at 0°C. After 20 minutes, corannulene (0.650g, 0.0026 mol) is added and stirred for 2
days. The solution turned from yellow to orange upon addition of corannulene. The solution
was then slowly washed with water and 10% aqueous hydrochloric acid and separated with
CH2Cl2. The organic layer was dried over magnesium sulfate and evaporated to yield a green oil. The product was then separated using an automated column of 100% CH2Cl2 and ramping
down to 99:1 CH2Cl2/EtOAc. The first peak is 1,5-diacetylcorannulene (9) (0.2372, 27%) and
1 the second peak is 1,8-diacetylcorannulene (10) (0.390g, 45%). (9) H NMR (400 MHz, CDCl3)
δ 8.662 (d, 1H, J = 6.4 Hz), 8.639 (d, 1H, J = 6.4 Hz) 8.513 (s, 1H), 8.481 (s, 1H), 7.873 (m, 4H),
13 2.849 (s, 6H). C NMR (400 MHz, CDCl3) δ 199.567, 199.405, 137.932, 136.640, 136.369,
35 136.241, 136.046, 134.712, 134.058, 133.258, 132.215, 131.768, 129.561, 129.271, 128.906,
128.551, 128.483, 128.319, 128.290, 127.964, 127.593, 127.325, 28.418, 28.389. (10) 1H NMR
13 (400 MHz, CDCl3) δ 8.456 (s, 1H), 8.289 (s, 1H), 7.652 (m, 2H), 2.786 (s, 3H). C NMR (400
MHz, CDCl3) δ 199.303, 137.670, 135.945, 134.641, 133.546, 132.740, 132.300, 129.476,
128.301, 127.978, 127.766, 127.372, 28.446.
Synthesis of 1,5 Dichlorovinylcorannulene (11)
To a mixture of 1,5-diacetylcorannulene (0.1832g, 0.548 mmol) and anhydrous dichloroethane (20mL), 1,2-phenylene phosphorotrichloridite (1.08g, 0.00439 mol) was added while refluxing under nitrogen for 18 hours. The solution was then quenched with water,
separated, dried over magnesium sulfate, and evaporated to yield a yellow solid (0.1871g, 92%).
1 13 H NMR (400 MHz, CDCl3) δ 8.015 (m, 4H), 7.737 (m, 4H), 5.895 (d, 4H). C NMR (400
MHz, CDCl3) δ 137.873, 137.628, 137.326, 136.099, 135.996, 135.407, 134.828, 134.669,
130.919, 129.689, 129.667, 128.551, 128.307, 127.721, 127.637, 127.428, 127.288, 127.236,
127.042, 126.782, 126.735, 126.616, 126.345, 118.094.
Synthesis of 1,8-dichlorovinylcorannulene (12)
To a mixture of 1,8-diacetylcorannulene (0.5835g, 0.00175 mol) and dry
dichloroethane (20mL), 1,2-phenylene phosphorotrichloridite (3.43g, 0.0139 mol) was added
while refluxing under nitrogen for 18 hours. The solution was then quenched with water,
separated, dried over magnesium sulfate, and evaporated to yield a yellow solid (0.5872g, 91%).
1 H NMR (400 MHz, CDCl3) δ 8.099 (s, 1H), 8.039 (s, 1H), 7.824 (m, 2H), 5.929 (d, 2H, J = 6
36 13 Hz). C NMR (400 MHz, CDCl3) δ 137.862, 137.118, 136.126, 135.321, 134.211, 131.239,
129.722, 128.315, 127.437, 127.245, 127.050, 126.830, 118.118.
Synthesis of 1,5-dialkynylcorannulene (13)
To a solution of diisopropylamine (1.45mL, 0.0104 mol) in THF, n-BuLi (6.32mL,
0.0101 mol) was added at –78°C under nitrogen and stirred for 20 minutes. 1,5-
dichlorovinylcorannulene was added slowly (0.1871g, 0.506 mmol, in THF) at that temperature
and stirred for 18 hours. The solution turned from yellow to orange upon addition of 1,5-
dichlorovinylcorannulene and to purple overnight. The solution was then quenched with water,
washed with 10% aqueous hydrochloric acid and extracted with CH2Cl2. The organic layer was
then dried over magnesium sulfate and evaporated to yield a yellow solid. The product was then
separated with an automated column using 100% cyclohexane to yield an orange product
1 (0.0758g, 50%). H NMR (400 MHz, CDCl3) δ 7.984 (m, 4H), 7.728 (m, 4H), 3.430 (s, 1H),
13 3.422 (s, 1H). C NMR (400 MHz, CDCl3) δ 135.642, 135.339, 135.263, 135.205, 134.801,
132.598, 132.267, 131.442, 131.326, 130.988, 130.231, 130.014, 127.706, 127.508, 127.173,
126.898, 126.272, 120.508, 120.208, 81.597, 81.565, 80.975, 80.930.
Synthesis of 1,8-dialkynylcorannulene (14)
To a solution of diisopropylamine (3.07mL, 0.02196 mol) in THF, BuLi (12.48mL,
0.01996 mol) was added at –78°C under nitrogen and stirred for 20 minutes. 1,8- dichlorovinylcorannulene was added slowly (0.7388g, 0.001996 mol, in THF) at that temperature and stirred for 18 hours. The solution turned from yellow to orange upon addition of 1,8-dichlorovinylcorannulene and to purple overnight. The solution was then quenched with
37 water, washed with 10% aqueous hydrochloric acid and extracted with CH2Cl2. The organic
ether layer was then dried over magnesium sulfate and evaporated to yield a yellow solid. The
product was then separated with an automated column using 100% cyclohexane to yield an
1 orange product (0.3312g, 56%). H NMR (400 MHz, CDCl3) δ 8.093 (s, 1H), 8.042 (s, 1H),
13 7.761 (m, 2H), 3.441 (s, 1H). C NMR (400 MHz, CDCl3) δ 135.755, 135.430, 134.949,
132.571, 131.671, 131.298, 130.125, 127.550, 127.045, 126.539, 120.293, 81.564, 80.955.
Synthesis of [6,6] 1,8-corannulene cyclophane (24)
To a solution of 1,2-cis dichloroethene (0.233mL, 0.00308 mol), Pd(PPh3)2Cl2 (0.2152g,
0.308 mmol), CuI (0.0585g, 0.308 mmol), and n-BuNH2 (25mL) was added dropwise 1,8-
dialkynylcorannulene (0.9148g, 0.00308 mol) in 20 mL THF 2ml/hr via a syringe pump. The
solution was stirred overnight at room temperature under nitrogen. The solution was washed
with H2O, and extracted with CH2Cl2. The organic layer was washed again with 10% HCl
solution and the organic layer was dried over MgSO4, and evaporated to yield a dark orange oil.
The oil was purified by column chromatography in which 4 peaks resulted. Peak 1 (12.4 mg,
0.67%), peak 2 (138 mg, 7.5%), and peak 3 (155 mg, 8.4%). Peak 2 – 1,8 bis-
1 chloroenynecorannulene (25): H NMR (400 MHz, CDCl3) δ 8.188 (s, 1H), 8.03 (s, 1H), 7.772
13 (m, 2H), 6.569 (d, 2H, 7.2 Hz), 6.255 (d, 2H, 7.2 Hz). C NMR (400 MHz, CDCl3) δ 135.531,
135.233, 134.739, 131.884, 131.432, 130.943, 130.059, 128.951, 127.459, 126.997, 126.728,
120.905, 112.260, 95.57, 87.22.
38 CHAPTER 4
SPECTRA
N O O N
O O
2
Figure 4.1 - 1NMR of 2,7-bis(diethylcarbamoyloxy)naphthalene (2)
39
N O O N
O O 2
Figure 4.2 – 13 C NMR of 2,7-bis(diethylcarbamoyloxy)naphthalene (2)
40 3
Figure 4.3 – 1H NMR of 2,7-dimethylnaphthalene (3)
41 3
Figure 4.4 – 13C NMR of 2,7-dimethylnaphthalene (3)
42 O O
4
Figure 4.5 – 1H NMR of 3,8-dimethylacenaphthenequinone (4)
43 O O
4
Figure 4.6 – 1H NMR of 3,8-dimethylacenapthenequinone (4) using high dilution
44 O O
4
Figure 4.7 – 13C NMR of 3,8-dimethylacenaphthenequinone (4)
45 5
Figure 4.8 – 1H NMR of 1,6,7,10-tetramethylfluoranthene (5)
46
5
Figure 4.9 - 13C NMR of 1,6,7,10-tetramethylfluoranthene (5)
47 Br Br Br Br Br Br Br Br
6
Figure 4.10 – 1H NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)
48 Br Br Br Br Br Br Br Br
6
Figure 4.11 – 13C NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)
49 Br Br
Br Br
7
Figure 4.12 – 1H NMR of 1,2,5,6-tetrabromocorannulene (7)
50 8
Figure 4.13 – 1H NMR of Corannulene (8)
51 * = CDCl3
*
8
Figure 4.14 –13C NMR of Corannulene (8)
52 O
O
9
Figure 4.15 – 1H NMR of 1,5-diacetylcorannulene (9)
53 O
O
9
Figure 4.16 – 13C NMR of 1,5-diacetylcorannulene (9)
54 O O
10
Figure 4.17 – 1H NMR of 1,8-diacetylcorannulene (10)
55 O O
10
Figure 4.18 – 13C NMR of 1,8-diacetylcorannulene (10)
56 Cl Cl
11
Figure 4.19 – 1H NMR of 1,5-bischlorovinylcorannulene (11)
57 Cl Cl
11
Figure 4.20 – 13C NMR of 1,5-bischlorovinylcorannulene (11)
58 Cl Cl
12
Figure 4.21 – 1H NMR of 1,8-bischlorovinylcorannulene (12)
59 Cl Cl
12
Figure 4.22 – 13C NMR of 1,8-bischlorovinylcorannulene (12)
60 13
Figure 4.23 – 1H NMR of 1,5-dialkynecorannulene (13)
61 13
Figure 4.24 – 13C NMR of 1,5-dialkynecorannulene (13)
62 14
Figure 4.25 – 1H NMR of 1,8-dialkynecorannulene (14)
63 14
Figure 4.26 – 13C NMR of 1,8-dialkynecorannulene (14)
64 Cl Cl
Figure 4.27 – 1H NMR of 1,8 bis-chloroenynecorannulene (25)
65 Cl Cl
Figure 4.28 – 13C NMR of 1,8 bis-chloroenynecorannulene (25)
66
Figure 4.29 – Electrospray MS of 1,8 bis-chloroenynecorannulene with AgBF3 (25)
67 APPENDIX A
Improvements on Corannulene Synthesis
The first part of my research concerns the optimization of the corannulene synthesis. Our starting material changed from a benzyl halide to 2,7-dihydroxynaphthalene into a better overall yield to obtain 2,7-dimethylnaphthalene. Treating 2,7-dimethylnaphthalene with oxalyl chloride and aluminum bromide gives us two isomers of 3,8-dimethyl-acenaphthenequinone and 4,7- dimethyl-acenaphthenequinone. The reaction is carried out at –15°C to give us selectivity with the desired isomer in a ratio of 3:1. Further work on separation of the isomers was carried out on deactivated alumina and able to be separated. Both isomers were carried out individually and carried on through the synthesis for further studies. The next step in the synthesis is an Aldol condensation with 3-pentanone followed by a Diels Alder and a retro Diels Alder with norbornadiene to give the tetramethylfluoranthene. This reaction proceeds in 58% yield with both isomers being present by NMR analysis. NBS bromination of the isomeric mixture of tetramethylfluoranthene to our surprise gave only the desired 1,6,7,10- tetrakis(dibromomethyl)fluoranthene. Once this step was carried out on 4,7-dimethyl- acenaphthenequinone separately, it was shown that multi-brominated products were recovered but not our desired compound. The next step in the synthesis is reaction with sodium hydroxide to form tetrabromocorannulene. Previously, completion of this step by vacuum filtration was done and used immediately in the following reduction step. Problems arose with this because our yields were lower than reported when we obtained corannulene. This could be due to the non-purity of the tetrabromocorannulene. Attempting crystallization using xylenes did not help the purity of our solution. Most of the tetrabromocorannulene did not go into xylenes and the
68 NMR showed no difference. Therefore the procedures were revised to slow addition of 1,6,7,10- tetrakis(dibromomethyl)fluoranthene to a solution of NaOH for single reduction of each molecule over a period of time, which seemed to improve yields of this step. The next step, a zinc reduction, proposed many problems because it required many equivalents of zinc being added and the purification from it was always difficult. Alternative solutions to the last reduction step have been carried out using two different palladium agents such as Pd(OAc)2,
42 43 Pd(dba)2, and (Ph3P)2PdCl2 with polymethylhydrosiloxane. NMR did not show pure
corannulene and the yields did not look any better than the zinc reduction. Also, a Nickel
44 complex shown to reduce halogens was tried using NaBH4 and ethanol. Results also showed
reduction of tetrabromocorannulene to corannulene but once again, yields were not improved.
So it was proved the zinc reduction is still the best way, so the next attempt was a high dilution
of the solvent ethanol to see if this could increase the yield. It turns out it did and the reaction
repeatedly proceeds in ~50% yield so the current synthesis is the zinc reduction in high dilution.
69 APPENDIX B
REFERENCES
1 Kroto, H. W.; Heath, J. R.; O'Brien, S. C.; Curl, R. F.; Smalley, R. E. Nature (London, United Kingdom) 1985, 318, 162-163. 2 David, W. I. F.; Ibberson, R. M.; Matthewman, J. C.; Prassides, K.; Dennis, T. J. S.; Hare, J. P.; Kroto, H. W.; Taylor, R.; Walton, D. R. M. Nature (London, United Kingdom) 1991, 353, 147-149. 3 Kraetschmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman, D. R. Nature 1990, 347, 354-358. 4 (a) Taylor, R.; Walton, D. R. M. Nature 1993, 363, 685. (b) Hirsch, A. Synthesis 1995, 895. 5 Clawson, P.; Lunn, P. M.; Whiting, D. A. J. Chem. Soc., Perkin. Trans. 1 1990, 169. 6 Ramaiah, D.; Rajadurai, S.; Das, P. K.; George, M. V. J. Org. Chem. 1987, 52, 1082. 7 Wang, G.; Yang, H.; Wu, P.; Miao, C.; Xu, Y.; J. Org. Chem. 2006, 71, 4346- 4348. 8 (a) S.H. Friedman, D.L. DeCamp, R.P. Sijbesma, G. Srdanov, F. Wudl, G.L. Kenyon, J. Am. Chem. Soc. 1993, 115, 6506-6509 (b) R. Sijbesma, G. Srdanov, F. Wudl, J.A. Gastoro, C. Wilkins, S.H. Friedman, D.L. DeCamp, G.L. Kenyon, J. Am. Chem. Soc. 1993, 115, 6510-6512. 9 Iijima, S. Nature (London, United Kingdom) 1991, 354, 56-58. 10 Scott, L. T.; Hashemi, M. M.; Bratcher, M. S. J. Am. Chem. Soc. 1992, 114, 1920-1921. 11 Lovas, F. J.; McMahon, R. J.; Grabow, J.-U.; Schnell, M.; Mack, J.; Scott, L. T.; Kuczkowski, R. L. J. Am. Chem. Soc. 2005, 127, 4345-4349. 12 (a) Barth, W. E.; Lawton, R. G. J. Am. Chem. Soc. 1966, 88, 380-381. (b) Lawton, R. G.; Barth, W. E. J. Am. Chem. Soc. 1971, 93, 1730-1745. 13 (a) Scott, L. T.; Hashemi, M. M.; Meyer, D. T.; Warren, H. B. J. Am. Chem. Soc. 1991, 113, 7082-7084. (b) Jones, C. S.; Elliott, E.; Siegel, J. S. Synlett 2004, 187-191. 14 Borchardt, A.; Fuchicello, A.; Kilway, K. V.; Baldridge, K. K.; Siegel, J. S. J. Am. Chem. Soc. 1992, 114, 1921-1923. 15 Ayalon, A.; Rabinovitz, M.; Cheng, P. C.; Scott, L. T. Angew. Chem. 1992, 104, 1691-1692. Angew. Chem., Int. Ed. Engl., 1992, 1631(1612), 1636-1697). 16 Baumgarten, M.; Gherghel, L.; Wagner, M.; Weitz, A.; Rabinovitz, M.; Cheng, P.- C.; Scott, L. T. J. Am. Chem. Soc. 1995, 117, 6254-6257. 17 Ayalon, A.; Sygula, A.; Cheng, P.-C.; Rabinovitz, M.; Rabideau, P. W.; Scott, L. T. Science 1994, 265, 1065-1067. 18 Kubozono, Y. Develop. Full. Sci. 2002, 3, 253-272. 19 Shu, C.-Y.; Gan, L.-H.; Wang, C.-R.; Pei, X.-l.; Han, H.-b. Carbon 2006, 44, 496- 500. 20 Warmuth, R. Angew. Chem. Int. Ed. Engl. 1997, 36, 1347-1350.
70
21 Cram, D. J.; Tanner, M. E.; Thomas, R. Angewandte Chemie 1991, 103, 1048- 1051 (See also Angew. Chem., Int. Ed. Engl., 1991, 1030(1048), 1024-1047). 22 (a) Mauser, H.; van Eikema Hommes, N. J. R.; Clark, T.; Hirsch, A.; Pietzak, B.; Weidinger, A.; Dunsch, L. Angew. Chem. Int. Ed. Engl. 1998, 36, 2835-2838. (b) Pietzak, B.; Weidinger, A.; Dinse, K. P.; Hirsch, A. Develop. Full. Sci. 2002, 3, 13-65. 23 Pietzak, B.; Weidinger, A.; Dinse, K. P.; Hirsch, A. Developments in Fullerene Science 2002, 3, 13-65. 24 Saunders, M.; Jimenez-Vazquez, H. A.; Cross, R. J.; Mroczkowski, S.; Gross, M. L.; Giblin, D. E.; Poreda, R. J. J. Am. Chem. Soc. 1994, 116, 2193-2194. 25 (a) Murata, Y.; Murata, M.; Komatsu, K. J. Am. Chem. Soc. 2003, 125, 7152- 7153. (b) Komatsu, K.; Murata, M.; Murata, Y. Science (Washington, DC, United States) 2005, 307, 238-240. 26 Seiders, T. J.; Baldridge, K. K.; O'Connor, J. M.; Siegel, J. S. J. Am. Chem. Soc. 1997, 119, 4781-4782. 27 Dunbar, R. C. J. Phys. Chem A. 2002, 106, 9809-9819. 28 Seiders, T. J.; Baldridge, K. K.; Grube, G. H.; Siegel, J. S. J. Am. Chem. Soc. 2001, 123, 517-525. 29 Dunbar, R. C. J. Phys. Chem A. 2002, 106, 9809-9819. 30 Jones, R. R.; Bergman, R. G. J. Am. Chem. Soc. 1972, 94, 660-661. 31 Petrukhina, M. A.; Andreini, K. W.; Mack, J.; Scott, L. T. Angew. Chem. Int. Ed. Engl. 2003, 42, 3375-3379. 32 B3LYP/6-31-G* using PC Spartan 2004 (Wavefunction Inc., Irvine CA>.) 33 Nath, M.; Huffman, J. C.; Zaleski, J. M. J. Am. Chem. Soc. 2003, 125, 11484- 11485. 34 Srinivasan, M.; Sankararaman, S.; Dix, I.; Jones, P. G. Org. Lett. 2000, 2, 3849- 3851. 35 http://www.doe.gov 36 Dillon, A. C.; Jones, K. M.; Bekkedahl, T. A.; Kiang, C. H.; Bethune, D. S.; Heben, M. J. Nature (London) 1997, 386, 377-379. 37 Scanlon, L. G.; Balbuena, P. B.; Zhang, Y.; Sandi, G.; Back, C. K.; Feld, W. A.; Mack, J.; Rottmayer, M. A.; Riepenhoff, J. L. J. Phys. Chem. B 2006, 110, 7688-7694. 38 Dallaire, C.; Kolber, I.; Gingras, M. Organic Syntheses 2002, 78, 42-50. 39 Jones, C. S.; Elliott, E.; Siegel, J. S. Synlett 2004, 187-191. 40 Seiders, T. J.; Elliott, E. L.; Grube, G. H.; Siegel, J. S. J. Am. Chem. Soc. 1999, 121, 7804-7813. 41 Sygula, A.; Xu, G.; Marcinow, Z.; Rabideau, P. W. Tetrahedron 2001, 57, 3637- 3644. 42 Viciu, M. S.; Grasa, G. A.; Nolan, S. P. Organometallics 2001, 20, 3607-3612. 43 Rahaim, R. J., Jr.; Maleczka, R. E., Jr. Tetrahedron Lett. 2002, 43, 8823-8826. 44 Stiles, M. Journal of Organic Chemistry 1994, 59, 5381-5385.
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