Radical Additions of Arenethiols to Ynamides for the Selective Synthesis of N-[(Z)-2-(Arylsulfanyl)-1-alkenyl]amides

Abstract

A variety of ynamides undergo highly regio-and stereoselective radical addition of arenethiols with the aid of triethylborane as a radical initiator. The products, N-[(Z)-2-arylsulfanyl-1-alkenyl]amides, can be reduced with triethylsilane in trifluoroacetic acid to yield N- [2-(arylsulfanyl)alkyl]amides.

Thiyl Radicals in Organic Synthesis

“…10 mol %) of Et 3 B as radical initiator. The nature of the arenethiyl radical (electron-rich vs electron-poor substituted aryl group) had a dramatic influence on the course of the reaction (Scheme ). , Whereas electron-poor arenethiols (Ar = Ph, p -BrC 6 H 4 , C 6 F 5 ) gave excellent yields, electron-rich arenethiols (Ar = p -MeOC 6 H 4 , p -MeC 6 H 4 , o -MeC 6 H 4 ) afforded the addition products in only low yields (<35%) as expected from their slow rate of addition onto alkynes (see section ). On the other hand, alkanethiols proved to be far less reactive, and the addition, which required prolonged time in refluxing benzene with AIBN as an initiator, is of little synthetic value in this case.…”

Copper-Catalyzed Regio- and Stereoselective Hydrothiolation of Allenamides, Enamides, and Ynamides

“…We then turned our interest toward the reactivity of ynamides with thiols in the presence of a copper catalyst. For these substrates, only a few examples of hydrothiolation have been reported, proceeding exclusively via radical pathways and hence leading to the β-thioethers . To the best of our knowledge, aryl-substituted ynamides have not yet been described in this reaction.…”

Ynamides in Free Radical Reactions

“…In 2009, Yorimitsu and Oshima reported the first addition of thiyl radicals to ynamides 52 [28,29] (Scheme 18). The 1‐amino‐2‐thio‐1‐alkenes 53 are obtained with moderate to excellent yields and the Z stereoisomer is the major one (usually above a 96:4 Z:E ratio).…”