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).
Preparation of Propargylic Sulfinates and their [2,3]-Sigmatropic Rearrangement to Allenic Sulfones
作者:Rama Rao Tata、Carissa S. Hampton、Michael Harmata
DOI:10.1002/adsc.201600986
日期:2017.4.3
scope of the [2,3]‐sigmatropic rearrangement of propargylic sulfinates to allenic sulfones by silver catalysis was expanded. A series of new propargylic sulfinate esters was generated from a variety of aromatic and heteroaromatic sulfonyl chlorides and their rearrangement to allenic sulfones is reported. In addition, the synthesis of propargylic sulfinate esters containing electron‐withdrawing benzenesulfonyl
Copper(I) bromide-promoted reactions of bromo[(diethoxyphosphoryl)difluoromethyl]zinc reagent 2 with propargylic tosylates and acetates were examined. The reaction proceeded in an SN2′ manner to give allenic (α,α-difluoromethylene)phosphonates in good to excellent yield.