A new approach to the synthesis of 2-vinylthiophenes and selenophenes; competition between free radical and anionic cycloaromatization of bridged di- and tetrapropargylic sulfides and selenides
作者:Yossi Zafrani、Marina Cherkinsky、Hugo E Gottlieb、Samuel Braverman
DOI:10.1016/s0040-4020(03)00327-2
日期:2003.4
presence of t-BuOK in dry THF these compounds underwent isomerization to the corresponding diallenes, followed by a tandem anionic cyclization and aromatization to 2-vinylthiophene or selenophene derivatives. Some mechanistic studies indicated competition between freeradical and anionic cycloaromatization. The latter is influenced by the nature of the bridging heteroatom, substitution of the allenyl group
Tandem rearrangement, cyclization and aromatization of sulfur bridged propargylic systems
作者:Samuel Braverman、Yossi Zafrani、Hugo E Gottlieb
DOI:10.1016/s0040-4039(00)00221-5
日期:2000.4
The reactivity of some novel pi-conjugated bis-propargylic sulfides, sulfoxides and sulfones under basic conditions has been investigated. These compounds undergo isomerization to the corresponding diallenes, followed by a tandem cyclization and aromatization of the latter via a diradical intermediate. Surprisingly, we have found that the rate of the cyclization step was independent of the nature of the bridging functionality. (C) 2000 Elsevier Science Ltd. All rights reserved.
Base catalyzed rearrangement of π-conjugated sulfur and selenium bridged propargylic systems
作者:Samuel Braverman、Yossi Zafrani、Hugo E Gottlieb
DOI:10.1016/s0040-4020(01)00923-1
日期:2001.10
A series of novel π-conjugated bis-propargylic sulfides, selenides, sulfoxides and sulfones have been prepared. In the presence of amine bases these compounds underwent facile isomerization to the corresponding allenes, followed by a tandem cyclization and aromatization of the latter via a diradical intermediate. While the reactions of sulfones and sulfoxides were almost spontaneous and proceeded in