Organoselenium- and proton-mediated cyclization reactions of allylic amides and thioamides. Syntheses of 2-oxazolines and 2-thiazolines
摘要:
A variety of allylic amides and thioamides were treated with phenylselenenyl bromide in chloroform to give, via 5-exo cyclization, 2-oxazolines and 2-thiazolines, respectively, carrying a (phenylselenenyl)methyl substituent in the 5-position. In some cases (N-crotyl- and N-cinnamylamides/thioamides), dihydro-1,3-oxazines/-thiazines were formed via 6-endo cyclization. The phenylselenenyl group of the cyclofunctionalization products was slowly eliminated by treatment with m-chloroperbenzoic acid to introduce unsaturation in the resulting oxazoline/thiazoline. Reductive removal of the phenylselenenyl group was effected by treatment with triphenyltin hydride. This reaction was sometimes accompanied by a rearrangement of the heterocyclic ring. Proton-induced cyclizations of allylic thioamides to give 2-thiazolines was slowly but efficiently effected in boiling toluene containing a catalytic amount of p-toluenesulfonic acid.
Electrochemical oxidative cyclization of olefinic carbonyls with diselenides
作者:Zhipeng Guan、Yunkun Wang、Huamin Wang、Yange Huang、Siyuan Wang、Hongding Tang、Heng Zhang、Aiwen Lei
DOI:10.1039/c9gc02665g
日期:——
The tandem cyclization of olefinic carbonyls with easily accessible diselenides facilitated by electrochemical oxidation has been successfully developed, which provides an environmentally friendly method for the construction of C–Se and C–O bonds simultaneously. A series of seleno dihydrofurans and seleno oxazolines, bearing fragile heterocycles, subtle C–I bonds and supernumerary vinyl groups, were