Sequential diastereoselective addition and palladium(II)-catalyzed allylic acetate transposition of syn- and anti-.alpha.-acetoxy-.beta.-silyl-(E)-hex-4-enoates with achiral acetals. Asymmetric synthesis of differentiated syn and anti 1,3-diol synthons
摘要:
syn- and anti-methyl alpha-acetoxy-beta-(dimethylphenylsilyl)-(E)-hex-4-enoates, (2R,3R)-8a and (2S,3R)-8b, undergo highly diastereo- and enantioselective addition reactions with aldehydes and acetals 11 catalyzed by the action of trimethylsilyl trifluoromethanesulfonate (TMSOTf) generating alpha-acetoxy-beta,-gamma-unsaturated esters (allylic acetates) 12. A subsequent allylic acetate transposition promoted by dichloropalladium bisacetonitrile complex, PdCl2(MeCN)2 afforded the differentiated 1,3-diol synthons 13.
Stereoselective Synthesis of (<i>Z</i>)- and (<i>E</i>)-Allylic Silanes by Copper-Mediated Substitution Reactions of Allylic Carbamates with Grignard Reagents
作者:Jacqueline H. Smitrovich、K. A. Woerpel
DOI:10.1021/jo991312r
日期:2000.3.1
Both (Z)- and (E)-allylic silanes were prepared with high stereoselectivity by the copper-mediated substitution of allylic carbamates by organometallic reagents. The reaction of alkylmagnesium reagents with (E)-allylic carbamates provides (Z)-allylic silanes, whereas both alkylmagnesium and alkyllithium reagents react with (Z)-allylic carbamates to afford (E)-allylic silanes. Because Grignard reagents
Lipase mediated resolution of chiral (E)-vinylsilanes: an improved procedure for the production of (R)- and (S)-(E)-1-trialkylsilyl-1-buten-3-ol derivatives
作者:Michelle A. Sparks、James S. Panek
DOI:10.1016/s0040-4039(00)79869-8
日期:1991.8
A crude enzymic extract of Pseudomonas AK in pentane catalyzes the transesterification of chiral (E)-vinylsilanes 1, resulting in the production of highly enantiomerically enriched (R)- and (S)-(E)-1-trialkylsilyl-1-buten-3-ol derivatives (S)-2 and (R)-3. A series of related vinylsilanes and two-different lipases have been screened to identify optimal reaction conditions.