Catalytic Asymmetric Di Hydroxylation
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A Concise Review on Phthlazine Derivatives and Its Biological Activities
Aswathy. J et al /J. Pharm. Sci. & Res. Vol. 11(7), 2019, 2526-2532 A Concise Review on Phthlazine Derivatives and its Biological Activities Aswathy. J M.Pharm, Department of Pharmaceutical Chemistry, Ezhuthachan College of Pharmaceutical Sciences, Marayamuttom Neyyattinkara, Trivandrum, India-695124 Abstract Phthalazine has good attention in the field of research study due to its wide spectrum of biological activity and therapeutic applications. Phthalazine is a good lead compound for the synthesis of novel drugs. There is a growing interest in the synthesis of several phthalazines derivatives as better drug candidates for the treatment of various diseases. Phthalazine contains a strong pharmacophoric moiety and ring structure it attracts the researchers to this nucleus for the synthesis of novel drugs. Through this review, introduce a new way for a researcher by introducing this nucleus and develop a novel class of drugs who have a better therapeutic profile. In this review, mainly discuss the different pharmacological activity of phthalazine which has already discussed by the researcher. These reports have resulted in a great number of contributions in diverse areas of interest. This study may produce a new way for the researchers to design and develop the phthalazine derivatives with good pharmacological activities. Keywords: Anticancer drug, anticonvulsant activity, antimicrobial agent, phthalazine and tuberculosis. INTRODUCTION activities of phthalazine (figure 1) and phthalazin-1(2H)- Phthalazine is a nitrogen-containing heterocyclic one (figure 2), encouraged us for the designing of new compound. Several research studies are focused on the molecules [1]. phthalazine nucleus due to their wide applicability. Phthalazine derivatives are promising drug candidate for PHARMACOLOGICAL ACTIVITIES OF PHTHALAZINE the treatment of various diseases. -
Recent Developments in Chemistry of Phthalazines
stry: Cu i rre em n t El-Azm et al., Organic Chem Curr Res 2015, 4:1 h R C e c s i e n a DOI: 10.4172/2161-0401.1000132 a r Organic Chemistry c g r h O ISSN: 2161-0401 Current Research ResearchReview Article Article OpenOpen Access Access Recent Developments in Chemistry of Phthalazines Fatma SM Abu El-Azm*, Mahmoud R Mahmoud, and Mohamed H Hekal Chemistry Department, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt Abstract This review highlights the methods used for the synthesis of phthalazine derivatives and fused phthalazinones. Their reactivity and synthetic importance were investigated. Phthalazine derivatives can be used as building blocks for heterocycles as well as fused heterocyclic compounds. Keywords: Phthalazine derivatives; Pyrazolophthalazines; were tested [59]. An expeditious one-pot method has been developed Indazolophthalazines; [1,2,4] Triazolophthalazines for the synthesis of aryl, heteryl thiadiazinyl-phthalazin-1,4-diones via a multicomponent approach. Reaction of phenacyl bromides 22 with Introduction thiocarbohydrazide 23 and phthalic anhydride afforded corresponding Among a large variety of nitrogen-containing heterocyclic aryl thiadiazinyl-phthalazine-1,4-diones 24 similarly, reaction of compounds, heterocyclic containing hydrazine has received 3-(2-bromoacetyl) coumarins 25 with thiocarbohydrazide and phthalic considerable attention because of their pharmacological properties anhydride afforded required heterylthiadiazinyl-phthalazine-1,4- and clinical applications [1-6]. Phthalazine derivatives were reported diones 26 under the same reaction conditions in excellent yields [60] to possess anticonvulsant [7-10], cardiotonic [11], antitumor [12-16], (Scheme 6). antihypertensive [17-19], antithrombotic [20], a ntidiabetic [21,22], Hydrazines with 2-acyl benzoic acids: Kirill et al. -
Organic Seminar Abstracts
Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/organicsemin1971752univ / a ORGANIC SEMINAR ABSTRACTS 1971-1972 Semester II School of Chemical Sciences Department of Chemistry- University of Illinois Urbana, Illinois 3 SEMINAR TOPICS II Semester 1971-72 Reactions of Alkyl Ethers Involving n- Complexes on a Reaction Pathway 125 Jerome T. Adams New Syntheses of Helicenes 127 Alan Morrice Recent Advances in Drug Detection and Analysis I36 Ronald J. Convers The Structure of Carbonium Ions with Multiple Neighboring Groups 138 William J. Work Recent Reactions of the DMSO-DCC Reagent ll+O James A. Franz Nucleophilic Acylation 1^2 Janet Ollinger The Chemistry of Camptothecin lU^ Dale Pigott Stereoselective Syntheses and Absolute Configuration of Cecropia Juvenile Horomone 1U6 John C. Greenfield Uleine and Related Aspidosperma Alkaloids 155 Glen Tolman Strategies in Oligonucleotide Synthesis 162 Graham Walker Stable Carbocations: C-13 Nuclear Magnetic Resonance Studies 16U Moses W. McMillan Organic Chlorosulfinates 166 Steven W. Moje Recent Advances in the Chemistry of Penicillins and Cephalosporins 168 Ronald Stroshane Cerium (iv) Oxidations 175 William C. Christopfel A New Total Synthesis of Vitamin D 18 William Graham Ketone Transpositions 190 Ann L. Crumrine - 125 - REACTIONS OF ALKYL ETHERS INVOLVING n-COMPLEXES ON A REACTION PATHWAY Reported by Jerome T. Adams February 2k 1972 The n-complex (l) has been described as an intermediate on the reaction pathway for electrophilic aromatic substitution and acid catalyzed rearrange- ment of alkyl aryl ethers along with sigma (2) and pi (3) type intermediates. 1 ' 2 +xR Physical evidence for the existence of n-complexes of alkyl aryl ethers was found in the observation of methyl phenyl ononium ions by nmr 3 and ir observation of n-complexes of anisole with phenol. -
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Journal of Pharmaceutical Research International 27(6): 1-15, 2019; Article no.JPRI.44928 ISSN: 2456-9119 (Past name: British Journal of Pharmaceutical Research, Past ISSN: 2231-2919, NLM ID: 101631759) An Overview of Different Synthetic Routes for the Synthesis of Phthalazine Derivatives Smita Singh1,2 and Nitin Kumar3* 1IFTM University, Muradabad, Uttar Pradesh, India. 2K. N. Modi Institute of Pharmaceutical Education and Research, Modinagar, Uttar Pradesh, India. 3Department of Pharmacy, Sushant School of Health Sciences, Ansal University, Gurugram, 122003, India. Authors’ contributions This work was carried out in collaboration between both authors. Both authors read and approved the final manuscript. Article Information DOI: 10.9734/JPRI/2019/v27i630189 Editor(s): (1) Dr. Carlos M. Contreras, Unidad Periferica Xalapa, Instituto de Investigaciones Biomedicas, UNAM, Mexico and Instituto de Neuroetologia, Universidad Veracruzana, Mexico. (2) Dr. Jinyong Peng, Professor, College of Pharmacy, Dalian Medical University, Dalian, China. (3) Dr. Ali Nokhodchi, Professor of Pharmaceutics and Drug Delivery, School of Life Sciences, University of Sussex, UK. Reviewers: (1) Sangeetha A/P Arullappan, Jalan Universiti, Malaysia. (2) Manojit Pal, University of Hyderabad, India. (3) B. Satish Jadhav, Balbhim College, India. Complete Peer review History: http://www.sdiarticle3.com/review-history/44928 Received 14 October 2018 Review Article Accepted 31 December 2018 Published 08 June 2019 ABSTRACT This review paper describes the different synthetic routes used for the synthesis of substituted phthalazine derivatives. Phthalazines have been used as building blocks for the synthesis of a new molecule with heterocyclic structure. These new molecules are highly useful in medicinal chemistry for the researchers leading to the further development of new molecules which have potency and effectiveness to produce a desired pharmacological response. -
Dissociation Constants of Organic Acids and Bases
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES This table lists the dissociation (ionization) constants of over pKa + pKb = pKwater = 14.00 (at 25°C) 1070 organic acids, bases, and amphoteric compounds. All data apply to dilute aqueous solutions and are presented as values of Compounds are listed by molecular formula in Hill order. pKa, which is defined as the negative of the logarithm of the equi- librium constant K for the reaction a References HA H+ + A- 1. Perrin, D. D., Dissociation Constants of Organic Bases in Aqueous i.e., Solution, Butterworths, London, 1965; Supplement, 1972. 2. Serjeant, E. P., and Dempsey, B., Ionization Constants of Organic Acids + - Ka = [H ][A ]/[HA] in Aqueous Solution, Pergamon, Oxford, 1979. 3. Albert, A., “Ionization Constants of Heterocyclic Substances”, in where [H+], etc. represent the concentrations of the respective Katritzky, A. R., Ed., Physical Methods in Heterocyclic Chemistry, - species in mol/L. It follows that pKa = pH + log[HA] – log[A ], so Academic Press, New York, 1963. 4. Sober, H.A., Ed., CRC Handbook of Biochemistry, CRC Press, Boca that a solution with 50% dissociation has pH equal to the pKa of the acid. Raton, FL, 1968. 5. Perrin, D. D., Dempsey, B., and Serjeant, E. P., pK Prediction for Data for bases are presented as pK values for the conjugate acid, a a Organic Acids and Bases, Chapman and Hall, London, 1981. i.e., for the reaction 6. Albert, A., and Serjeant, E. P., The Determination of Ionization + + Constants, Third Edition, Chapman and Hall, London, 1984. BH H + B 7. Budavari, S., Ed., The Merck Index, Twelth Edition, Merck & Co., Whitehouse Station, NJ, 1996. -
Synthesis of Novel Series of Phthalazine Derivatives As Potential Antitumor Agents
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by International Institute for Science, Technology and Education (IISTE): E-Journals Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 Synthesis of Novel Series of Phthalazine Derivatives as Potential Antitumor Agents Ashraf Farouk Wasfy *, Aly Abdelmaboud Aly, Mohamed Sayed Behalo, Nora Sobhi Mohamed Chemistry department, Faculty of science, Benha University Benha, Egypt. P.O. Box 13518 Tel.: +2.010.1599607Fax: +2.013.3222578 E-mail address: [email protected] (Nora Sobhi) e-mail: [email protected] Abstract: A novel series of phthalazine derivatives bearing isoindol-1,3-dione moiety were synthesized by treating 2-[4-(4- chlorophthalazine-1-yl)phenyl]-1H-isoindole-1,3-(2 H)-dione 3 with various chemical reagents.The newly synthesi- zed compounds were characterized on the basis of their spectral ( 1H NMR, 13 C NMR, Ms, IR) analyses. In vitro , most of the synthesized derivatives were screened for their antitumor activity against HepG2 cells using MTT assay. Compounds 11, 18 and 19c showed the most potent cytotoxic effect concluded from their IC 50 values 217.4, 240.3 and 234.5 µg/ml respectively. Key Words: Phthalazin-1-(2 H)-One; chlorophthalazine; isoindol-1,3-dione; antitumor activity. 1. Introduction: Nitrogen-containing heterocycles possesses diverse chemotherapeutic activities [1,2] . Among a large variety of nitrogen-containing heterocyclic compounds, phthalazin-1(2 H)-ones, they were reported to be used as efficient antitumors [3] and therapeutic agents [4] . N-(4-Chlorophenyl)-4-(pyridin-4-ylmethyl)phthalazin-1- amine, also known as Vatalanib has been shown to serve as anticancer agent (Fig.1) . -
The Catalytic Hydrogenation of Benzodiazines
THE CATALYTIC HYDROGENATION OF BENZODIAZINES: I. PHTHALAZINE II. QUINAZOLINE A Dissertation Presented to the Department of Chemistry Brigha~ Young University In Partial Fulfillment of the Requirements for the Degre~ Doctor of Philosophy by Danny Lee Elder August 1969 This dissertation, by Danny Lee Elder, is accepted in its present form b y the Department of Chemistry of Brigham Young University as satisfying the dissertation requirement for the degree of Doctor of Philosophy. ii . , TO Lynette, David, and Douglas iii ACKNOWLEDGEMENTS Deep appreciation is expressed to Dr. H. Smith Broadbent, without whose friendly association, patient help, and kindly ex- · tended advice this research problem could not have been carried out. Gratitude is also expressed £or the many extra-academic endeavors Dr. Broadbent has made on my behalf. Appreciation is extended to the Department of Chemistry of Brigham Young University for financial support in the form of teaching and research assistantships. My wife deserves special thanks for her encouragement, patience, understanding, and especially, for making it all worth- while. Finally, sincere thanks go to a great group of fellow-graduate students--Craig Argyle, Weldon Burnham, Vic Mylroie, Wes Parish, and Walter Sudweeks--for helpful discussions, comrade- ship, and most of all, for the memorable hours spent at such places as Anderson Lake, Four-Lakes Basin, Klondike Bluff, and of course, "Organic Pass, 11 (Grosebeck Pass). iv TABLE OF CONTENTS Chapter Page I. INTRODUCTION • • • • • • • • • • • • • • • 1 II. LITERATURE REVIEW • • • • • • • • • • • • 4 Phthalaz~ne • • • • . 4 Structure and properties • • • • • • • • • · 4 Synthesis of phthalazine • • • • • • • • • 8 Reduced phthalazines • • • • • • • • • • 10 Quinazoline • • • • • • . 12 Structure and properties • . • 12 Synthesis of quinazoline • • • • • 15 Reduced quinazolines • • • • 18 Catalytic Hydrogenation of Benzoazines and Benzodiazines • • • • • • • • 20 Quinoline . -
Bridging Mcmurry and Wittig in One-Pot
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1755 Bridging McMurry and Wittig in One-Pot Olefins from Stereoselective, Reductive Couplings of Two Aldehydes via Phosphaalkenes JURI MAI ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 ISBN 978-91-513-0536-3 UPPSALA urn:nbn:se:uu:diva-368873 2019 Dissertation presented at Uppsala University to be publicly examined in Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, Friday, 15 February 2019 at 10:15 for the degree of Doctor of Philosophy. The examination will be conducted in English. Faculty examiner: Professor Dr. Christian Müller (Freie Universität Berlin, Institute of Chemistry and Biochemistry). Abstract Mai, J. 2019. Bridging McMurry and Wittig in One-Pot. Olefins from Stereoselective, Reductive Couplings of Two Aldehydes via Phosphaalkenes. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1755. 112 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-513-0536-3. The formation of C=C bonds is of great importance for fundamental and industrial synthetic organic chemistry. There are many different methodologies for the construction of C=C bonds in the literature, but currently only the McMurry reaction allows the reductive coupling of two carbonyl compounds to form alkenes. This thesis contributes to the field of carbonyl olefinations and presents the development of a new synthetic protocol for a one-pot reductive coupling of two aldehydes to alkenes based on organophosphorus chemistry. The coupling reagent, a phosphanylphosphonate, reacts with an aldehyde to yield a phosphaalkene intermediate which upon activation with a base undergoes an olefination with a second aldehyde. A general overview of synthetic methods for carbonyl olefinations and the chemistry of phosphaalkenes is given in the background chapter. -
Essentials of Heterocyclic Chemistry-I Heterocyclic Chemistry
Baran, Richter Essentials of Heterocyclic Chemistry-I Heterocyclic Chemistry 5 4 Deprotonation of N–H, Deprotonation of C–H, Deprotonation of Conjugate Acid 3 4 3 4 5 4 3 5 6 6 3 3 4 6 2 2 N 4 4 3 4 3 4 3 3 5 5 2 3 5 4 N HN 5 2 N N 7 2 7 N N 5 2 5 2 7 2 2 1 1 N NH H H 8 1 8 N 6 4 N 5 1 2 6 3 4 N 1 6 3 1 8 N 2-Pyrazoline Pyrazolidine H N 9 1 1 5 N 1 Quinazoline N 7 7 H Cinnoline 1 Pyrrolidine H 2 5 2 5 4 5 4 4 Isoindole 3H-Indole 6 Pyrazole N 3 4 Pyrimidine N pK : 11.3,44 Carbazole N 1 6 6 3 N 3 5 1 a N N 3 5 H 4 7 H pKa: 19.8, 35.9 N N pKa: 1.3 pKa: 19.9 8 3 Pyrrole 1 5 7 2 7 N 2 3 4 3 4 3 4 7 Indole 2 N 6 2 6 2 N N pK : 23.0, 39.5 2 8 1 8 1 N N a 6 pKa: 21.0, 38.1 1 1 2 5 2 5 2 5 6 N N 1 4 Pteridine 4 4 7 Phthalazine 1,2,4-Triazine 1,3,5-Triazine N 1 N 1 N 1 5 3 H N H H 3 5 pK : <0 pK : <0 3 5 Indoline H a a 3-Pyrroline 2H-Pyrrole 2-Pyrroline Indolizine 4 5 4 4 pKa: 4.9 2 6 N N 4 5 6 3 N 6 N 3 5 6 3 N 5 2 N 1 3 7 2 1 4 4 3 4 3 4 3 4 3 3 N 4 4 2 6 5 5 5 Pyrazine 7 2 6 Pyridazine 2 3 5 3 5 N 2 8 N 1 2 2 1 8 N 2 5 O 2 5 pKa: 0.6 H 1 1 N10 9 7 H pKa: 2.3 O 6 6 2 6 2 6 6 S Piperazine 1 O 1 O S 1 1 Quinoxaline 1H-Indazole 7 7 1 1 O1 7 Phenazine Furan Thiophene Benzofuran Isobenzofuran 2H-Pyran 4H-Pyran Benzo[b]thiophene Effects of Substitution on Pyridine Basicity: pKa: 35.6 pKa: 33.0 pKa: 33.2 pKa: 32.4 t 4 Me Bu NH2 NHAc OMe SMe Cl Ph vinyl CN NO2 CH(OH)2 4 8 5 4 9 1 3 2-position 6.0 5.8 6.9 4.1 3.3 3.6 0.7 4.5 4.8 –0.3 –2.6 3.8 6 3 3 5 7 4 8 2 3 5 2 3-position 5.7 5.9 6.1 4.5 4.9 4.4 2.8 4.8 4.8 1.4 0.6 3.8 4 2 6 7 7 3 N2 N 1 4-position -
PDF (Chapter 1)
Chapter 1–Evolving Strategies Toward the Synthesis of Curcusone C 1 CHAPTER 1 Evolving Strategies Toward the Synthesis of Curcusone Ci 1.1 INTRODUCTION AND ALTERNATE SYNTHETIC STRATEGIES 1.1.1 INTRODUCTION Indigenous to Central America, the flowering plant Jatropha curcas has traditionally been used in the manufacturing of soaps and lamp oil but has also drawn attention due to its potential applications in the biodiesel industry.1 J. curcas has also received notice by organic chemists owing to its structurally diverse array of diterpenoid secondary metabolites, which includes the curcusone (i) This research was a collaborative effort between A. C. Wright and C. W. Lee, see: reference 6, reference 19, and reference 20. Chapter 1–Evolving Strategies Toward the Synthesis of Curcusone C 2 family of natural products. This family comprises various synthetically challenging and biologically active rhamnofolane diterpenoid natural products. In 1986, Naengchomnong and coworkers first isolated curcusones A–D (1–4, Figure 1.1.1) and elucidated the structures of 2 and 3 via X-ray diffraction.2 Over the ensuing three decades, several more members of this family were structurally identified and were further discovered to possess anticancer activity.3 Among them, curcusone C (3) demonstrates the most potent and varied anticancer properties, including anti- proliferative activity against human hepatoma (IC50 in 2.17 uM), ovarian carcinoma (IC50 in 0.160 2 uM), and promyeolycytic leukemia (IC50 in 1.36 uM). Figure 1.1.1. Reported Structures of Curcusones A–J O O H O H H H H H R2 H Me Me R1 HO MeO O O O R1, R2 = Me, H : Curcusone A (1) Curcusone E Curcusone F R1, R2 = H, Me : Curcusone B (2) R1, R2 = Me, OH : Curcusone C (3) R1, R2 = OH, Me : Curcusone D (4) O O O H H H H H H H R2 O OH R1 O OH MeO O O O Curcusone G Curcusone H R1, R2 = Me, H : Curcusone I (5) R1, R2 = H, Me : Curcusone J (6) Despite these enticing biological features, 3 and all of its structural relatives have yet to surrender to any total synthesis campaigns. -
A Convenient Access to Thienyl-Substituted Phthalazines 1245 M
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Universidade do Minho: RepositoriUM Nov-Dec 2005 A Convenient Access to Thienyl-substituted Phthalazines 1245 M. Manuela M. Raposo,a* Ana M. B. A. Sampaioa and G. Kirschb a Centro de Química, Universidade do Minho, Campus de Gualtar 4710-057 Braga, Portugal b Laboratoire d'Ingénierie Moléculaire et Biochimie Pharmacologique, UFR SciFA/Université de Metz, 1, Boulevard Arago, Metz Technopôle, 57078 Metz Cedex 3, France Received November 3, 2004 A synthesis of 1-alkoxy- and 1-amino- substituted 4-(2-thienyl)-phthalazines is described from halo- derivatives of 4-(2-thienyl)-1-(2H)-phthalazinone 3. J. Heterocyclic Chem., 42, 1245 (2005). Introduction. Chlorine, bromine and triflate thienyl-substituted phtha- The practical interest upon phthalazine derivatives is lazines 4 and 5 were synthesized in order to be used as pre- based on their widespread applications [1-4]. Phthalazines, cursors on the synthesis of 1-alkoxy- and 1-amino-phtha- like others members of the isomeric diazine series, have lazines 6-7. These derivatives could also be used in the found wide applications as therapeutic agents [2,5-28]. future, as coupling components in palladium catalyzed Phthalazines are also commonly used as ligands in transi- cross-coupling reactions to obtain more complex mole- tion metal catalysis, [29-34] as chemiluminescent materi- cules with potential applications in NLO [52]. For this als [35-38] and for optical applications [39]. kind of application the substitution of the phenyl ring by Despite their significance, there are only a limited num- the thiophene ring was already demonstrated to be very ber of routes for the synthesis of phthalazines. -
Title Synthetic Studies on the Chemistry of Gem-Dimetalation with Inter-Element Compounds( Dissertation 全文 )
Synthetic Studies on the Chemistry of gem-Dimetalation with Title Inter-element Compounds( Dissertation_全文 ) Author(s) Kurahashi, Takuya Citation Kyoto University (京都大学) Issue Date 2003-03-24 URL http://dx.doi.org/10.14989/doctor.k10168 Right Type Thesis or Dissertation Textversion author Kyoto University Synthetic Studies on the Chemistry ofgem-Dimetalation with Inter-element Compounds Takuya Kurahashi 2003 Synthetic Studies on the Chemistry ofgem-Dimetalation with Inter-element Compounds Takuya Kurahashi 2003 Contents Chapter 1 Introduction and General Summary 1 Chapter 2 Silylborylation and Diborylation of Alkylidene-type Carbenoids. Synthesis of 1-Boryl-1-silyl-1-alkenes and 1,1-Diboryl-1-alkenes 21 Chapter 3 Stereospecific Silylborylation of a-Chloroallyllithiums. Synthesis and Reactions of Allylic gem-Silylborylated Reagents 53 Chapter 4 Synthesis and Reactions of 1-Silyl-1-borylallenes 81 Chapter 5 Efficient Synthesis of 2,3-Diboryl-1,3-butadiene and Synthetic Applications 95 List ofPublications - 115 Acknowledgments - 117 Abbreviations Ac acetyl J coupling constant in Hz Anal. element analysis LDA lithium diisopropylamide aq. aqueous m multiplet (spectral) Bn benzyl M mol per liter Bpin 4,4,5,5-tetramethyl-I,3,2-dioxabolan-2-yl Me methyl brs broad singlet (spectral) MEM 2-methoxyethoxymethyI Bu butyl min minute(s) calcd calculated mL mililiter cat. catalytic mp melting point Cy cyclohexyl Ms mesyl d doublet (spectral) NMR nuclear magnetic resonance dba dibenzylideneacetone Pent pentyl DME 1,2,-dimethoxyethane Ph phenyl DMF N,N-dimethylformamide