Preparation of polyfunctional allenic alcohols by the regioselective addition of functionalized propargylic chromium(III) organometallics to carbonyl compounds
摘要:
The reaction of propargylic halides 1 (X = Cl, Br) with an aldehyde or ketone (0.67 equiv) in the presence of CrCl2 (2.0 equiv) and LiI (2 equiv, necessary if X = Cl) affords allenic alcohols 3 with excellent regioselectivities (3-6% of the regioisomeric acetylenic alcohol 4 is formed) and in good yields (68-90%). Interestingly, this method allows the generation of highly functionalized intermediate propargylic chromium organometallics contained an ester, cyano, or chloride functionality. The alpha-alkyl-substituted propargylic bromide 10 reacts with benzaldehyde yielding the acetylenic alcohol 11 as a diastereomeric mixture of only one regioisomer (90% yield).
Carbonyl Allenylations andPropargylations by 3-Chloro-1-propyne or 2-Propynyl Mesylateswith Tin(IV) Chloride and Tetrabutylammonium Iodide
作者:Yoshiro Masuyama、Akiko Watabe、Yasuhiko Kurusu
DOI:10.1055/s-2003-41012
日期:——
By the use of tin(IV) chloride and tetrabutylammonium iodidein dichloromethane, 3-chloro-1-propyne or 2-propynyl mesylate canbe applied to allenylation and propargylation of aldehydes (carbonylallenylation and propargylation) to produce a mixture of 1-substituted2,3-butadien-1-ols and 1-substituted 3-butyn-1-ols. 1-Substituted2-propynyl mesylates selectively cause carbonyl propargylation,while 3-substituted 2-propynyl mesylates cause carbonyl allenylation.