selective dehydrohalogenation to form alpha-haloacrylate analogues. A variety of alpha-halo Michael acceptors were prepared in dimethyl sulfoxide under mild, base-free conditions, including the preparation of alpha-bromoacrolein and alpha-chloro- and bromoacrylonitriles. Synthesis of these molecules has been reported in the literature to be difficult. Among all the existing dehydrohalogenation procedures
Tandem Oxidation/Halogenation of Aryl Allylic Alcohols under Moffatt−Swern Conditions
作者:Jiandong Yin、Christina E. Gallis、John D. Chisholm
DOI:10.1021/jo0711992
日期:2007.8.31
Aryl allylic alcohols are converted to halogenated unsaturated ketones or allylic halides using excess Moffatt−Swern reagent. Electron-poor aromatic rings favor formation of the halogenated ketone, while electron-donating substituents in the ortho or para positions favor formation of the allylic halide. The oxidation/halogenation reaction performs well with both oxalyl chloride and oxalyl bromide,
Chiral aziridination of cyclic α-bromoenones is achieved by the use of the lithium salt of (S S )-(+)-p-toluenesulfinamide, which leads to products with diastereomeric excesses in the range of 30―65% using a simple protocol. A key factor associated with chiral induction is the incorporation of the reacting olefin in a cycle, indicating the importance of conformational restriction in the reacting double
Enantioselective conjugate additions of in situ generated 2-alkoxycarbonyl-3(2H)-furanones to three distinct types of π-electrophiles (terminal alkynones, α-bromo enones, and α-benzyl nitroalkenes) are reported. Catalysis by a nickel(II)–diamine complex provided alkynone-derived adducts with high enantioselectivity, preferentially as the Z-isomers, and completely suppressed the undesired O-alkylation