(S,S)-N,N-Bis(-α-methylbenzyl)formamide is the first example of chiral formamides that function as Lewis base catalysis to effectively serve catalytic asymmetricsynthesis. The chiral formamide in combination with an additive, HMPA, catalyzes allylations of aliphatic aldehydes with allyl- and crotyltrichlorosilanes with high enantioselectivity (up to 98% ee). In the crotylations with (E)-crotyltrichlorosilane
Asymmetric synthesis via acetal templates. 9. Further studies of the allylation reaction. Preparation of (−)-dihydromyoporone
作者:William S. Johnson、Peter H. Crackett、John D. Elliott、Jacek J. Jagodzinski、Stephen D. Lindell、S. Natarajan
DOI:10.1016/0040-4039(84)80038-6
日期:——
A procedure has been developed for the high-yield coupling of chiral acetals 1 with allyltrimethylsilane (2, R′=H) as well as with methallyltrimethylsilane (2,R′=ME) to afford the hydroxy ethers 3 in which the new chiral center is formed highly enantioselectively. Homoallylic alcohols 4 of high ee are produced by removal of the chiral auxiliary.
Asymmetric synthesis via acetal templates. 3. On the stereochemistry observed in the cyclization of chiral acetals of polyolefinic aldehydes; formation of optically active homoallylic alcohols
作者:Paul A. Bartlett、William S. Johnson、John D. Elliott