Catalytic asymmetric allylation chiral amide

Nitrene transfer to selenide is also possible. Catalytic asymmetric induction in this process has been studied with Cu(OTf)/bis(oxazoline) catalyst (Scheme 22). When prochiral selenide 206 and TsN=IPh are allowed to react in the presence of Cu(OTf)/chiral bis(oxazoline) 122b, selenimide 207 is obtained with enantioselectivity of 20-36% ee. When arylcinnamyl selenide 208 is applied to this reaction, corresponding selenimide 209 is produced which undergoes [2,3]-sigmatropic rearrangement to afford chiral allylic amides 211 in up to 30% ee. 

The catalytic asymmetric rearrangement of functionalized cyclohexene and cyclopentene oxides to give chiral allylic alcohols has been studied using sub-stoichiometric amounts of a chiral lithium amide in combination with a stoichiometric amount of different lithiated imidazoles (Scheme 47).79... 

Sddergren, M.J. and Anderson, PG. (1998) New and high enantioselective catalysts for the rearrangement of mejo-epoxides into chiral allylic alcohols. Journal of the American Chemical Society, 120, 10760-10761 S6dergren, M.J., Bertilsson, S.K. and Anderson, P.G. (2002) Allylic alcohols via catalytic asymmetric epoxide rearrangement. Journal of the American Chemical Society, 122, 6610-6618 Bertilsson, S.K. and Anderson, P.G. (2002) Asymmetric base-promoted epoxide rearrangement achiral lithium amides revisited. Tetrahedron, 58, 4665-4668. 

Two further contributions illustrate how chiral lithium amides can be used as catalysts in asymmetric deprotonation reactions (Schemes 2 and 3). The first example of catalytic chiral lithium amide chemistry was reported [13] by Asami (Scheme 2). In this process an achiral base, in this case LDA, provides a stoichiometric reservoir of amidoli-thium reagent. However, deprotonation of the epoxide is affected primarily by the chiral lithium amide 11 rather than the relative excess of LDA. Turnover is possible since the resulting chiral secondary amine 10 can be deprotonated by the remaining reservoir of LDA thus regenerating the chiral base 11. For example, the deprotonation of cyclohexene oxide 8 in the presence of DBU as an additive gives the allylic alcohol 9 in 74 % ee (82 % yield) using 50 mol% of chiral base 11. 

The asymmetric 1,3-dipolar cycloaddition of nitrones instead of nitrile oxides was also realized The nitrones 7 possessing an amide moiety were reacted with allylic alcohols 1 (R, R = H) by the use of a catalytic amount of (R,R)-DIPT as a chiral auxiliary to afford the corresponding 3,5-cw-isoxazolidines 8 with high regio-, diastereo-, and enantioselectivity up to over 99% ee (Eq. 11.5). This asymmetric 1,3-dipolar cycloaddition was applied to the synthesis for the (25,4R)-4,5-dihydroxynorvaline derivative 10, which is a key component of polyoxin E, via amino alcohol intermediate 9 (Scheme 11.3) [12]. 

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