LAUSR

The synthesis of unprecedented benzimidazole-fused thiazocines, thiazonines, and thiazecines having an exocyclic double bond is reported. The process consists in an 8-, 9-, or 10-exo-dig cyclocarbopalladation followed by reduction. The scope and limitations were established and showed the importance of the precursor structure for the success of the reaction. A competition between the exo-dig and the endo-dig cyclization was observed for two substrates bearing an N-homopropargyl chain, the endocyclization leading to rarely encountered 10and 11-membered N,Sheterocycles with a trans-endocyclic double bond. X-ray structures of three products were obtained by co-crystallization with fumaric acid and show the twisted structures of these molecules.