Angewandte Chemie International Edition: 1993 02/15/20 1
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Baran Group Meeting Kelly J. Eberle Angewandte Chemie International Edition: 1993 02/15/20 1 January 1993: A Timeline Hot topics: 1993: In Chemistry -Fullerenes Martin Luther King Jr. Day February -Porphyrins observed in all 50 states NH N -!-lactam antibiotics -Electron Transfer Reactions World Trade Center bombing in N HN New York City (1992 Nobel Prize Winner, Rudolph Marcus of Caltech) March Nobel Prize in Chemistry 1993: Baby born April DNA-Based Chemistry in NJ -Kary Mullis (PCR) ‘Walker, Texas -Michael Smith (oligonucleotide-based, site-directed Ranger’ TV debut mutagenesis) May ACIEE ’93 Top Authors: Volume 32 Dietmar Stalke (9) Budweiser commercial dog June Spuds Mackenzie dies 12 Issues Waldemar Adam (6) 654 articles Roland Boese (6) Steven Spielberg’s Jurrasic Park Arnold Rheingold (6) premieres in theaters Paul Schleyer (6) July Most cited articles (not including reviews) Pfaltz et al, 566 (630) Golfer Jack Nicklaus wins the US Chiral Phosphinoaryldihydrooxazoles as Ligands in Asymmetric Senior Open by one stroke August Catalysis: Pd‐Catalyzed Allylic Substitution Ruth Bader Ginsburg sworn in Meijer et al, 1308 (488) as US Supreme Court Justice Poly(propylene imine) Dendrimers: Large‐Scale Synthesis by September Hetereogeneously Catalyzed Hydrogenations Lehn et al, 69 (315) ‘Seinfeld’ wins Emmy for October Multicomponent Self‐Assembly: Spontaneous Formation of a Cylindrical Outstanding Comedy Series Complex from Five Ligands and Six Metal Ions Nelson Mandela and F. W. deKlerk Lehn et al, 703 (301) awarded Nobel Peace Prize Self‐Assembly, Structure, and Spontaneous Resolution of a Trinuclear November Triple Helix from an Oligobipyridine Ligand and NiII Ions Herrmann et al, 1157 (266) Snoop Dogg releases December debut album ‘Doggystyle’ Methyltrioxorhenium(VII) as Catalyst for Epoxidations: Structure of the Active Species and Mechanism of Catalysis NASA STS-61 mission launches Endeavour to repair Hubble Telescope 4 TSRI papers: Boger, Ghadiri, Sharpless, Nicolaou (review, The Battle of Calicheamicin ") Baran Group Meeting Kelly J. Eberle Angewandte Chemie International Edition: 1993 02/15/20 2 Enantioselective synthesis: # Amino Acids and Acetals Direct Addition of Grignard to Diketone Bartoli et al, 1061 R2 Enders et al, 418 -limited to primary Grignards R1 Me R O N N O O 1. CeCl3, THF, 0 °C O R3 EtO SAMP RAMP OH O O Mg H2N H2N 2. R3MgX, -30 °C H X SAMP OMe OMe R1 Me R1 Me Ce Cl OEt 70-85% 89% R2 R2 Cl Cl Raney Ni/H 2 Head-to-tail alkyne coupling Barluenga et al, 893 N RM/CeCl3 N MeOH NH2 N -100 °C HN 70-100 °C EtO via: I OMe OMe R EtO 72-98% EtO 62-83% R R H R OEt I 1:2 Ipy BF /HBF 2 4 4 I I OEt OEt de 78-98%, ee 90-96% 96-99% after chromatography R DCM, -80 °C 1. MeLi/CeCl3 -100 °C 70-80% R I I C 2. CH COCl, -78 °C R 52% 3 3. Li/NH3 4. ethylene glycol, PPTS One-Pot Propargylic Alcohol Synthesis Hwu et al, 608 O 1. nBuLi then Boc2O R’Li OH O 2. N2H4, MeOH NHBoc NH2 neat, 25 °C HN Me 3. O TMSI 3 O HO Ph R’ HO Me Me H NR2 O 74%, 3 steps 88% Ph 74-93% Me O O R=Me, Et, iPr, Bu O 97% ee 95% ee O O R’ H2O Enantioselective Aldols Enders et al, 421 NR2 H pdt Et Et H NR2 H R’ Et Et Ph Ph OMe OMe 1. BOMCl, 1. LDA/LiBr, -78 °C DIPEA,TBAI BOMO O Titanated Methoxyallene as Homoaldol Equivalent Reissig et al, 1449 N 2. RCHO, -90 to -78 °C N 2. chromat. OAr R O N R 1. nBuLi, -40 °C R OH then H2O/NH4Cl OH N 3.O3, -78 °C 91:1 ":$ OAr O 2. ClTi(OiPr)3 Me OAr ● ● Bn N H 84-97% R 73-86% >98% ee -100 to -78 °C 2 Bn2N OMe O 78-98% de O H OMe -78 to -40 °C (OiPr)3Ti OMe HCl H ~50% Synthesis of C2-symmetric HIV-1 Protease Inhibitors Enders et al, 423 R O LiN(TMS) 2 2 steps O BnI SAMP chemistry O RAMP chemistry H 11 steps 11 steps Bn2N R O OH OH de, ee = 98% de, ee = 98% OH Ph HN O Bn2N Ph Ph O O Ph Ph R N homostatine lactone BocHN NHBoc Me Me BocHN NHBoc AlMe NBn2 O 3 Baran Group Meeting Kelly J. Eberle Angewandte Chemie International Edition: 1993 02/15/20 3 Tandem Epoxy-Hydroxylation Adam et al, 733 OH OH Asymmetric Dihydroxylation: Ti(OiPr) OH 4 HO HO Where are we in the [2+2] vs. [3+2] Debate? (0.05 equiv) Me Me 1980: Original report by Sharpless, proposing [2+2] HOO O + O Me DCM, -25 °C, 1989: Corey proposes [3+2] pathway Me Me 1989-1996: Several back and forth publications between the groups OH 85%, < 5 min Me February 1997: Sharpless publishes Hammet analysis supporting [2+2] 95:5 Ti Ti October 1997: Sharpless (with Houk and Singleton) publishes conclusive Me O2, TPP, hv O DCM, 0 °C O O O evidence for [3+2] (KIE studies support a symmetrical TS) Me Me + Me H Temperature Effects on Asymmetric Dihydroxylation TPP = H H H vs. Me Sharpless et al, 1329 tetraphenylporphyrin OH Ti(OiPr) Me Me 4 1. OsO , L HOO (0.1 equiv) 4 Me 2. LAH OH DCM, -25 °C, OH OH R’ R R’ Me 80%, 8h HO HO R Me + Me 95:5 OH O O Me ODHDQ 90:10 d.r. Me Me N Catalytic epoxidation with Methyltrioxorhenium Herrmann et al, 1157 4: R=R’=C4H9 -First isolated peroxo-metal complex stable to H2O and H2O2 L 5: R=Ph, R’=H 6: R=C8H17, R’=H O -Inversion point in Eyring plot H O O O Proposed [3+2] Pathway: Me 2 2 Re O suggests reaction proceeds (1 equiv) O Re O H2O2 O O O R R with at least two Re Me O O O O O O O Me O enantioselective steps H H 80% O Os Os O H H O -Depending on T, either can be Compound A O O MTO isolable solid L R L R rate-determining -Compound A does not react (supports [2+2] mech) H2O2 Proposed [2+2] Pathway: with alkenes (excess) 1:1 O -Reaction does not work with metal:alkene O organoperoxides, suggesting O R O Os O O O -25 °C + Os O R that peroxo ligand essential for Compound O R O O O + Os epoxidation A O O R R R Os O R O O R Kinetic Resultion of chiral hydroperoxides by Horseradish Peroxidase -L L -L L -L L Adam et al, 1737 OH scope includes: OH OOH O R O O R OMe OOH O O OOH R O O O O Os O O Os + Os Os Ph Me Ph Me MeO2C O O Me/Et O O O Ph Me (R) (S) R R R R L R L L L HRP both in >99% ee Baran Group Meeting Kelly J. Eberle Angewandte Chemie International Edition: 1993 02/15/20 4 Metathesis of Sulfur-containing Olefins Basset et al, 112 Synthesis of Ferrocenyl Derivatives with Planar Chirality Kagan et al, 568 -Starting material synthesis J. Org. Chem. 1991, 56, 5991 SMe SMe Me O tBu Et2O Ph Ph tBuMgCl ferrocenyl- S 1-5 mol% cat Me SMe Me Ph Me Ph lithium PhCl -78 °C nBuLi W Cl 20 to 80 °C O OH Fe 20% 95% Me O 75% O 80% O OAr S O S O SMe tBu 0.4 mol% cat Me Li tBu Ph2P tBu PhCl O tBu O O catalyst S 80 °C S S S Ph Ph PCl 88% S MeI 2 Fe Fe Fe 80% 80% 1 mol% cat PPh2 SR PhCl ROMP 20 to 80 °C SR Tantalum complexes as Phospha-Wittig Reagents Schrock et al, 756 Review on this method: Power, 850 >96% conversion >97% conversion LiPHPh Ph faster rates for bulkier R TMS P TMS Et2O, -78 °C Et2O, -40 °C Li3(N3N) + TaCl5 [(N3N)TaCl2] N N crystallize crystallize Ta 3 (N3N is amine TMS N Structure and reactivity of Fe % -allyl hydrido complexes 32% 87%, stable N McMahon et al, 1073 ligand w/ TMS groups) H tBu O CO OC hv TMS O Fe CO Ph 83% PPh OC Fe H OC Fe H P N H tBu N TMS CO + Ta CO OC CO OC CO TMS N exo endo H tBu N Carbenerhodium complexes Werner et al, 1480 Previous attempt by Perego et al (J. Chem. Soc. Dalton Trans. 1977, 1828) This work: Ph Ph showed loss of CPh2 upon heating i i Pr3Sb CPh2N2 Pr Sb PiPr3 i 3 Pr3P Rh Rh Ph 96% Rh Ph Cl i Cl i 98% Cl i i N Sb Pr3 Sb Pr i CPh2N2 Pr3P Pr3P 3 P Pr3 i N2CPh2 & N RhCl(P Pr3)2 Rh Rh target Cl i Cl i NaC5H5 P Pr3 P Pr3 Rh Ph ~75% i Pr3Sb Ph Baran Group Meeting Kelly J. Eberle Angewandte Chemie International Edition: 1993 02/15/20 5 Water-soluble phosphine ligands Stelzer et al, 1058 Selective C2 functionalization of imidazole ring of histidine Evans et al, 1326 SO2Cl Method from synthesis of dipthamide SO3K Initial Observation: SO3K J. Am. Chem. Soc. 1992, 114, 1495-1496 1. Dowex-H+ I KOH PH3 N Ph NHBoc 3 equiv N 2. NaOH NHBoc DMSO/KOH, P 3 I N CO tBu PdCl2(PPh3)2 Ph F 60% H 2 N CO tBu F CuI, TEA H 2 65 °C, 52% acetylene acts as reductant For Ruhrchemie/Rhone-Poulenc process SO3Na Scope: (industrial synthesis of aldehydes via formylation, Rh-catalyzed) BocN NHBoc BocN NHBoc R 2 equiv -also works for primary and secondary phosphine SM P 3 I R PdCl (PPh ) N CO2tBu N CO tBu 2 3 2 2 CuI, TEA, RT R = Bu, tBu, TMS Chiral Phosphinooxazoline Ligands for Pd Catalysis yields 83-98% from mono-iodo SM Pfaltz et al, 566 (most cited paper in ACIE 1993) Application to Zn: O BocN 1.