Highly (E)-selective wadsworth-emmons reactions promoted by methylmagnesium bromide

Organic Letters

Volumn 10, Issue 23, 2008, Pages 5437-5440

  Claridge, Timothy D W ^a   Davies, Stephen G ^a   Lee, James A ^a   Nicholson, Rebecca L ^a   Roberts, Paul M ^a   Russell, Angela J ^a   Smith, Andrew D ^a   Toms, Steven M ^a  

^a UNIVERSITY OF OXFORD   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 59949097919     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol802212e     Document Type: Article

References (40)

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26. iPrMgBr to promote the reaction gave only modest levels of diastereoselectivity under a variety of conditions, although in an isolated case the stereoselective formation of the corresponding (Z)-olefin isomer [(Ε):(Z) ratio 5:95] was noted; see: Sano, S.; Ando, T.; Yokoyama, K.; Nagao, Y. Synlett 1998, 777.
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29. The anion derived from deprotonation of phosphonate 1 with MeMgBr was noted to be much less reactive toward olefination of an aldehyde than the corresponding anion derived from deprotonation of phosphonate 1 with BuLi.
30. 2O (3 × 10 mL). The combined organic extracts were washed with brine (15 mL), dried over magnesium sulfate, and concentrated in vacuo to give (Ε)-α,β- unsaturated ester 5 as a colorless oil (163 mg, 98%. (Ε):(Z) > 180:1).
31. Claridge, T. D. W.; Davies, S. G.; Polywka.; M, E. C.; Roberts, P. M.; Russell, A. J.; Savory, E. D.; Smith, A. D. Org. Lett. 2008, 10, 5433 (o1802211p)
32. Deprotonation of ethyl 4-phenylbut-2-enoate and subsequent reprotonation has been shown to lead preferentially to the corresponding (Ε)-β, γ-unsaturated ester; see: Guha, S. K.; Shibayama, A.; Abe, D.; Sakaguchi, M.; Ukaji, Y.; Inomata, K. Bull. Chem. Soc. Jpn. 2004, 77, 2147.
33. Katayama, M.; Nagase, R.; Mitarai, T.; Misaki. T.; Tanabe, Y. Synlett 2006, 129.
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36. In accordance with this hypothesis olefination of the corresponding trans-dioxolane containing aldehyde mediated by BuLi or under Masamune-Roush conditions gave (Ε)-α,β-unsaturated ester 62 as a single diastereoisomer.
37. Bach, J.; Bull, S. D.; Davies, S. G.; Nicholson, R. L.; Sanganee, H. J.; Smith, A. D. Tetrahedron Lett. 1999, 40, 6677.
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39. For selected examples of the application of this methodology in synthesis, see: Davies, S. G.; Hunter, I. A.; Nicholson, R. L.; Roberts, P. M.; Savory. E. D.; Smith, A. D. Tetrahedron 2004, 60, 7553.
40. Davies, S. G.; Nicholson, R. L.; Smith, A. D. Org. Biomol. Chem. 2005, 3, 348.