An unprecedented chelation approach to activate C(sp)3-S bonds in nickel-catalyzed cross-coupling reactions is described. Our theme was based on the formation of a chelation complex which results in the enhancement of the reactivity of aliphatic carbon-sulfur bonds. When two dithioacetal functionalities are located in close proximity, selective olefination of one of these two dithioacetal groups can thus be achieved conveniently. Depending on the relative positions of the newly formed double bond and the remaining dithioacetal group, tandem olefination occurs to give the corresponding 1,5-bis-silyl-substituted pentadienes. Various neighboring heteroatom substituents (OR, OH, NR(2) as well as SR groups) can facilitate the olefination of a dithioacetal group. Poly(thioether) linkage afforded the corresponding degradation products via a B-sulfur elimination process. 1,3-Dimercapto- and 1,3-dithiolatopropanes furnish the cyclopropane formation under nickel-catalyzed reaction conditions. The reaction of a dihydrothiopyran with MeMgI in the presence of the nickel catalyst proceeds via a sulfur-coordinated ir-allyl complex, which can further activate the CS bond to give vinylcyclopropane.
A chelation approach toward activation of Csp3-S bonds. Nickel-catalyzed selective cross coupling of bisdithioacetals with Grignard reagents
作者:Ken Tsung Wong、Tien Yau Luh
DOI:10.1021/ja00044a060
日期:1992.8
Chelation Assisted Conversion of C-S Bonds into C-C Bonds
作者:Tien-Yau Luh
DOI:10.1080/10426509708545523
日期:1997.1.1
species, one of these carbon-heteroatom bonds can be activated. This strategy has been applied for the nickel-catalyzedcrosscoupling reactions of certain rigid bisdithioacetals. Heteroatom substituents such as hydroxy, methoxy or amino groups also assist the alkenation of aliphatic dithioacetals; and homoallylic alcohols, ethers and amines are respectively obtained in reasonably good yields Polythioethers