The propargyltitanium reagents derived from 1-alkylpropyne condensed with aldehydes to give α-allenyl alcohol regioselectively, while the allenyltitanium reagents generated from 1-alky1-1-butyne derivatives gave threo-β-acetylenic alcohols with high regio- and stereoselectivities. The course of the reaction was determined by the substitution pattern of starting alkynes. The similar reactions of metallated
obtained by the reaction of 3-bromo-1-butyne (11) with tributylstibine. The corresponding stiborane (13) reacted with aldehyde to give acetylenic alcohol (14) exclusively in good yield, and the diastereoselectivity was moderately in favour of the threo isomer in the presence of MgBr2. All of the reactions had good chemoselectivity for aldehyde.
Silanes in organic syuthesis. 11. Regiocontrolled synthesis of α-hydroxymethylated (trimethylsilyl)allenes
作者:Rhys G. Daniels、Leo A. Paquette
DOI:10.1016/s0040-4039(01)90382-x
日期:1981.1
The organometallic produced by reaction of trimethylsilylpropargyl bromide with aluminum amalgam in anhydrous tetrahydrofuran condenses readily with aldehydes and ketones to give allenic alcohols resulting from coupling α to the trimethylsilyl substituent.
The reactions of trimethylsilylallylic organoantimonycompound with aldehydes show very high selectivity favoring α-adducts; and the reactions of trimethylsilylpropargylic organoantimonycompounds with aldehydes also exhibit very high acetylenic selectivity (α-adducts) in the presence of LiBr.