Alkyne Insertion Enabled Vinyl to Acyl 1,5‐Palladium Migration: Rapid Access to Substituted 5‐Membered‐Dihydrobenzofurans and Indolines

We herein report a novel 1,5-palladium/hydrogen shift pattern between a vinyl and an acyl group, which provides a divergent access to substituted 5-membered-dihydrobenzofurans and indolines. Further studies unveiled a novel relayed decarbonylative Catellani-type reaction. Mechanistic investigations including DFT calculations have shed light on the reaction pathway.

Abstract

“Through space” palladium/hydrogen shift is an efficient strategy to achieve selective functionalization of a specific remote C−H bond. Compared with relatively extensive exploited 1,4-palladium migration process, the relevant 1,5-Pd/H shift was far less investigated. We herein report a novel 1,5-Pd/H shift pattern between a vinyl and an acyl group. Through the pattern, rapid access to 5-membered-dihydrobenzofuran and indoline derivatives has been achieved. Further studies have unveiled an unprecedented trifunctionalization (vinylation, alkynylation and amination) of a phenyl ring through 1,5-palladium migration relayed decarbonylative Catellani type reaction. A series of mechanistic investigations and DFT calculations have provided insights into the reaction pathway. Notably, it was unveiled that the 1,5-palladium migration in our case prefers a stepwise mechanism involving a Pd^IV intermediate.

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