Search

The selective alkyl lithium-induced ring opening of 1,3-di-isopropylsilylenes is described. The reaction affords a differentially substituted 1,3-diol bearing a silane that resides at the oxygen in the more sterically demanding position. The reaction can be highly selective with a regiochemical preference up to >50:1 and likely proceeds via an alkoxy-silane intermediate. This intermediate can by trapped by methyl iodide to provide the corresponding silyl methyl ether, wherein the silane again resides at the oxygen in the more sterically demanding position.

[reaction: see text] The conversion of 1-(2-methoxyethoxy)ethyl-protected beta-hydroxy ketones to syn-1,3-ethylidene acetals is effected by Et(3)SiH and SnCl(4). This reaction is proposed to proceed via a cyclic oxocarbenium ion intermediate and provides the products in yields that range from 69 to 94% and with diastereoselectivities that are >200:1.