Journal Club Presentation by Remond Moningka 04/17/2006

Transcription

1 β-alkyl-α-allylation of Michael Acceptors through the Palladium-Catalyzed Three-Component Coupling between Allylic Substrate, Trialkylboranes, and Activated lefins Yoshinori Yamamoto, et al. J. rg. Chem. 2006, 71(6), Journal Club Presentation by emond Moningka 04/17/2006

2 utline Background information. General eaction and Mechanism. The Scope of π-allylpalladium Chemistry Using Activated lefins. Alkyl-allylation of Activated lefins through the Palladium-Catalyzed Three- Component Coupling. Conclusion. Future Direction. eferences.

3 Background Discovered by Prof. Jiro Tsuji in π- allylpalladium species could be substituted with certain nucleophiles, such as the anion of diethyl malonate and acetoacetate. Professor Barry M. Trost Followed by Prof. Barry Trost in He demonstrated that the allylation prefers the less substituted end of the π-allyl system. First Tsuji-type eaction CH 2 Cl H 2 C - th, DMS HC CH + HC C t CH 2 Cl H 2 C r.t = C Tsuji, J. Takashashi.H. Morikawa, M. Tetrahedron Lett t C Me CH t + C t n-c 3 H 7 Cl C 2 H 5 - CH-(C 2 C 2 H 5 ) 2 C 2 C 2 H 5 C 2 C 2 H 5 + C 2 C 2 H 5 C 2 C 2 H 5 + C2 H 5 2 C C 2 C 2 H 5 Trost, B.M. Fullerton, T.J. J. Am. Chem. Soc

4 Background Tsuji-Trost Allylation -catalyzed allylation of carbon nucleophile with allylic compounds via π-allylpalladium complexes. 1 (0) or (II) complexes (catalytic) solvent / phosphine ligand Base 1 (II) Nuc-H 1 Nuc = leaving groups = epoxides, carbonates, halogens ptically active substrate 1 2 (0) (cat) hard Nuc (0) (cat) soft Nuc inversion of configuration Nuc retention of configuration Nuc soft Nuc - = enamines, enolates, CH 2 C 2, CH 2, CH 2 S 2 Ph, CH 2 SPh. Laszlo Kurti, Barbara Czako. Strategic Applications of Named eactions in rganic Synthesis lsevier Inc.

5 Background General Tsuji-Trost Mechanism (0) or (II) complexes (precatalysts) Nuc L n (0) coordination Nuc (0) L n (0) L n substitution then reductive elimination oxidative addition Nuc - + L (II) L + L / - L ligand exchange (II) Laszlo Kurti, Barbara Czako. Strategic Applications of Named eactions in rganic Synthesis lsevier Inc.

6 Background Mechanism with soft and hard Nucleophiles 1 2 coordination and.a with inversion L n (0) 1 2 Nuc hard Nuc - 1 L n 2 soft Nuc Nuc transmetallation with retention then reductive elimination substitution with inversion then reductive elimination Laszlo Kurti, Barbara Czako. Strategic Applications of Named eactions in rganic Synthesis lsevier Inc.

7 The Scopes of Palladium-catalyzed Activated lefins arly works + H C "M" H C + H N "M" Hydrocarbonation H N Yamamoto, Y. et. J. Am. Chem. Soc. 1998, 120, Hydroamination Amphiphilic Catalytic Bis-πallylpalladium Complex Nu - L n + L n NC C C WG 1 WG 2 C C WG 1 WG 2 Nu Nu Yamamoto, Y. et. J. Am. Chem. Soc. 1997, 119, Yamamoto, Y. et. Tetrahedron Letters. 2000, 41,

8 The Scope Continued xa-π-allyl-π-allylpalladium WG WG Yamamoto, Y. et. J. rg. Chem. 1998, 63, WG WG [3+2] Cycloaddition. 3 "" Intermolecular version 1 H 2 Nu Nu-H =Y=Z Cycloaddition Y Yamamoto, Y. et. J. rg. Chem. 1998, 63, Z a: =N, Y=C, Z= b: =, Y=C, Z= c: =N, Y=C, Z=N 1 Paul A. Bartlett, James D. Meadows, ckhard ttow J. Am. Chem. Soc (18);

9 The Scope Continued Construction of Cyclopentene rings via [3+2] Cycloaddition "" II H Yamamoto, Y. et. J. rg. Chem. 1999, 64, Formation of Cyclic thers + H i Pr "" -C 2 Yamamoto, Y. et. J. rg. Chem. 2001, 66,

10 Palladium-Catalyzed eactions of Highly Activated lefins NC Cl TMS Cl SnBu 3 C N Cl 2 + NH =, NTs H i Pr

11 The palladium-catalyzed three component β-alkyl-α-allylation + 1 B (0),THF 40 o C, 6h 1 2 t 3 B + Ac (0), THF 40 0 C, 10h

12 Ligand Screen for the Alkyl-allylation eaction t 3 B + Ac (0), THF 40 0 C, 10h dba = dibenzylideneacetone Ph Ph dppm = bis(diphenylphosphino)methane Ph 2 P PPh 2 dppb = 1,4-bis(diphenylphosphino)butane Ph 2 P PPh 2 dppf = 1,1'-bis(diphenylphosphino) ferrocene Fe PPh 2 PPh 2 dppp = 1,3-bis(diphenylphosphino)propane Ph 2 P PPh 2

13 The role of Phosphine Ligands? Trialkylborane is usually not an alkylating agent unless if it coordinates to a Lewis base prior to the reaction. Coordination of borane species to a Lewis base (PPh 3 ) should result in the formation more reactive tetracoordinate boron ate complex I. Proven by 31 P NM spectroscopy, and is proposed to form a more nucleophilic alkylating agent. The formation of an aluminum ate complex II from trialkylaluminum is known. B Al PPh 3 I PPh 3 II Schneider, C. Brauner, J. ur. J. rg. Chem. 2001,

14 Alkyl-allylation of Various Activated lefins

15 Mechanism (0) Ac NC Ac NC t 2 BAc NC Bt 2 N C - (0) + (0) N C NC N + t 3 B

16 Conclusion A new procedure for the alkyl-allylation of activated olefins via the three-component coupling reaction has been established. The reaction generally proceeds under milder conditions (40 0 C) and with a high atom economy (catalytic amount of Palladium). (PPh 3 ) 4 is required for the reaction to proceed presumably that phosphine ligands are necessary to activate the boron species.

17 Future Work Catalytic Asymmetric Synthesis. Instead of using achiral phosphine ligands, various chiral phosphine ligands can be examined. t 3 B + 2 dba 3.CHCl 3, chiral ligand* NC Ct Ct Ac THF chiral ligand* NH HN PPh 2 Ph 2 P PPh 2 PPh 2 P P Trost ligand BINAP DuPHS

18 eferences Tsuji, J. Takashashi.H. Morikawa, M. Tetrahedron Lett Trost, B.M. Fullerton, T.J. J. Am. Chem. Soc Laszlo Kurti, Barbara Czako. Strategic Applications of Named eactions in rganic Synthesis lsevier Inc. Yamamoto, Y. et. J. Am. Chem. Soc. 1998, 120, Yamamoto, Y. et. J. Am. Chem. Soc. 1997, 119, Yamamoto, Y. et. Tetrahedron Letters. 2000, 41, Yamamoto, Y. et. J. rg. Chem. 1998, 63, Yamamoto, Y. et. J. rg. Chem. 1998, 63, Paul A. Bartlett, James D. Meadows, ckhard ttow. J. Am. Chem. Soc (18); Yamamoto, Y. et. J. rg. Chem. 1999, 64, Yamamoto, Y. et. J. rg. Chem. 2001, 66, Schneider, C. Brauner, J. ur. J. rg. Chem. 2001,

19 Thank you