Magnesiated unsaturated silylated cyanohydrins as synthetic equivalents of aromatic and heterocyclic grignard reagents bearing a ketone or an aldehyde.
[reaction: see text] The preparation of iodo-substituted aryl, heteroaryl, or cycloalkenyl ketones as silylated cyanohydrins allows the smooth performance of an I/Mg-exchange using i-PrMgCl.LiCl. A facile deprotection of the resulting functionalized products obtained by a reaction with electrophiles (acid chlorides, allylic bromide, benzylidene-p-toluenesulfonamide, and 3-iodocyclohexenone) produces polyfunctional ketones in good overall yields. This sequence can be extended to aromatic iodoaldehydes. In these cases, the deprotection of the silylated cyanohydrin functionality is best performed with aqueous CuSO(4) under basic conditions.
Department Chemie und Biochemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377 München, Germany.
Ching-Yuan
CY
Liu
Hongjun
H
Ren
Paul
P
Knochel