Conjugate Additions to Nitroalkenes

A variety of carbanions have been employed forthe conjugate addition to nitroalkenes recent results are shown in Table 4.1. 

Beak and co-workers have also produced the key alcohol intermediate 74 by the sparteine-mediated lithiation and conjugate addition of allylamines to nitroalkenes to give Z-enecarbamates in good yields with high enantio- and diastereoselectivty (Scheme 16). Thus treatment of the allylamine 87 with n-BuLi in the presence of (-)-sparteine followed by conjugate addition to nitroalkene 88 gave the desired enecarbamate 89 in... 

Conjugate addition to nitroalkenes anti-p-amfno alcoholsSodium benzyloxide undergoes anfi -selective conjugate addition to 2-nitro-2-butenes to give 2-... 

Scheme 7.22. En anti os elective conjugate addition to nitroalkenes.

Unusually concentrated efforts have been spent to optimizing the conjugate addition to nitroalkenes. Useful organocatalysts for ketones donors are 124, 125, and 105A. The unsymmetrical 3,3 -dimorpholine 62 (R = i-Pr) is targeted for use in the case of aldehydes. 

The enantioselective addition of dialkylzinc reagents to alkynyl aldehydes catalysed by ( )-(+)-(l-methylpyrrolidin-2-yl)diphenylmethanol has been described. Thus the laevorotatory alcohol 102 was obtained in 78% enantiomeric excess (equation 15). The action of diethylaluminium chloride on alkynyllithium compounds yields ether-free diethylalkynylalanes 103, which undergo conjugate addition to nitroalkenes (equation 16). Conjugate addition also occurs in the reactions of (l-alkynyl)diisopropoxyboranes 104 (R = Bu, t-Bu or Ph) with a,j5-unsaturated ketones 105 (R = H, Me or Ph R = Me, hexyl or Ph) (equation 17). ... 

McCooey, S.H., McCabe, T. and Connon, S.J. (2006) Stereoselective synthesis of highly functionalized nitrocyclopropanes via organocatal)4ic conjugate addition to nitroalkenes. The Journal of Organic Chemistry, 71, 7494-7497. 

As was the case for addition to enones, several halogen sources including NBS [279] and I2 [280] can promote conjugate addition to nitroalkenes. 

Scheme 36 Asymmetric conjugate addition to nitroalkene 151 in the synthesis of (—)-botryodiplodin (155)...

Alkylzincs undergo conjugate addition to nitroalkenes in the presence of a catalytic amount of (CuOTf)2 or [(MeCN)4Cu]PF6 with a chiral... 

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