Palladium-Catalyzed, Migratory Insertion of Isocyanides into C(Thiophene)‒SMe: a New Entry to Atom-Transfer Reactions

Something added, nothing removed. That is, a Pd(II)-catalyzed, CN directed addition of isocyanides to Csp2‒SMe bond of the in situ generated thiophenes effectively recycles the SMe activating group into thioimidate products. The catalytic sequence includes selective Csp2‒SMe bond activation/migratory insertion of isocyanides into Csp2‒Pd(IV), and following Csp2‒SMe bond forming reductive elimination from imidoyl‒Pd(IV)‒SMe complex. Through this transition-metal catalyzed addition reaction, we established isocyanides as a new template for atom-transfer reactions. This groundbreaking research lacks using the ancillary ligand that is a constant feature of all the previously reported addition reaction with C‒S bond. This reaction proceeds through a high-valent Pd(II)/(IV) catalytic cycle, which to our knowledge has not been previously reported in this regard. Also, isocyanide insertion into C(Ar)‒S bond through an addition reaction is unprecedented. Finally, the resulting thioimidates were realized to be a convenient precursors for synthesis of thieno[2,3-c]pyrrole by targeting the recycled SMe group for the second time via a cascade reaction.

from # & – All via ola Kala on Inoreader http://ift.tt/2vA6jQs

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