Abstract 1,1-Bis(trimethylsilyl)-2-propyne, prepared from propargyltrimethylsilane, was reacted, in the presence of a Lewis acid, with electrophiles (aldehydes, acetals) to afford (E)-silylated conjugated enynes.
The rearrangement of acetylenic epoxidesmediated by low-valence organotitanium and organozirconium reagents is reported to give conjugated enynes. Moderate to good yields and high selectivities are obtained when using the organozirconium(II) Negishi reagent in toluene at 20 °C; whereas only poor yields and low selectivities are achieved with the organotitanium(II) Sato reagent. The process is stereospecific
据报道,由低价有机钛和有机锆试剂介导的炔属环氧化物的重排得到共轭烯炔。在 20 °C 的甲苯中使用有机锆 (II) Negishi 试剂时,可获得中等至良好的产率和高选择性;而使用有机钛 (II) Sato 试剂只能实现低产率和低选择性。该过程是立体有择的,包括通过将低价钛和锆试剂氧化插入到炔环氧化物的碳碳三键中来形成二氧化钛和氧化锆环丙烯。这些金属环丙烯然后通过环氧化物开环重排以提供立体定义的炔丙基金属。共轭烯炔最终通过金属氧化物的β-消除产生。
Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
A straightforward synthesis of polyendiynes is described. The method is based upon a simple dimerization reaction of silylated enynes in the presence of copper salts. A variety of polyunsaturated compounds have been obtained in high yields and with high retention of configuration. (C) 1998 Elsevier Science S.A. All rights reserved.
Regio- and stereoselective cyclopropanation of functionalised dienes. Novel methodology for the synthesis of vinyl- and divinyl-cyclopropanes
作者:István E. Markó、Thierry Giard、Shinichi Sumida、Anne-Elisabeth Gies
DOI:10.1016/s0040-4039(02)00242-3
日期:2002.3
Dienes, bearing an electron-withdrawing substituent at C-1, are cyclopropanated regio- and stereo selectively at the C-C double bond proximal to this electron-withdrawing group. The highest selectivity is observed in the case of dienylboronates. The cyclopropanation of these substrates affords almost exclusively the synthetically useful 1-boronato-2-vinyl-cyclopropanes. (C) 2002 Elsevier Science Ltd. All rights reserved.