Regio‐ and Stereoselective Chlorocyanation of Alkynes

Abstract

Av ariety of terminal and internal alkynes were converted regio-and stereoselectively into (Z)-3-chloroacrylonitriles by treatment with BCl 3 in the presence of stoichiometric amounts of imidazolium thiocyanates.These products could be readily functionalizedt op rovide useful building blocks,t hus demonstrating the synthetic value of the method. Preliminary mechanistic studies suggest initial activation of the cationic thiocyanate by the Lewis acid, followed by electrophilic attack of the alkyne.The syn addition of achloride to the vinyl cation intermediate and final elimination of the thiourea unit afford the desired chloroacrylonitriles.Scheme 1. Synthesis of substituted acrylonitriles from alkynes.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Stereospecific Oxycyanation of Alkenes with Sulfonyl Cyanide

“…Based on this discovery, we then screened a series of Lewis acid catalysts as potential activators of TsCN. A series of boron Lewis acids such as BF 3 ⋅ OEt 2 , BCl 3 , and BBr 3 as well as the weak Lewis acid BPh 3 failed to promote the reaction (entries 2–5) [12] . Other group 13 Lewis acids were also ineffective for this reaction, even though gallium trihalides have previously been used in some electrophilic cyanation reactions (entries 6–10) [13] .…”

Alkyne Aminopalladation/Heck and Suzuki Cascades: An Approach to Tetrasubstituted Enamines

“…The dual functionalization of internal alkynes is an important method of generating tetrasubstituted double bonds. [1,2,3] For this purpose, either special reagents [4] have been designed or transition metal catalysts, especially those based on Pd, have been used. In many cases a carbopalladation of a C�C triple bond has been used, leading to a vinyl-Pd species.…”