Head-to-Tail Selective [2 + 2 + 2] Cycloadditions of Bisallenes Enabled by Ligand-Free Nickel(0)

Abstract

A ligand-free Ni(0) catalyst enables highly chemo- and regioselective [2 + 2 + 2] cycloadditions between 1,5-bisallenes and acetylenes, affording 6,6-fused hexahydroisoquinoline frameworks under mild conditions. DFT studies reveal that head-to-tail selectivity arises from competing oxidative cyclization pathways with metallacycle geometry dictating product formation. This work highlights how simple nickel complexes can achieve precise molecular construction without the need for ancillary ligands

We are grateful for the financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (Projects PID2023-146849NB-I00/MICIU/AEI/10.13039/ 501100011033/FEDER, UE, RED2022-134939-T, PID-2021-127423NB-I00, predoctoral FPU20/00707 grant to R.M.-C., and Margarita Salas Grant (NextGenerationEU) to S.C.D.K.),a Beatriu de Pinós−AGAUR Postdoctoral Grant (2022 BP00051) to A.S., and the Generalitat de Catalunya (Project 2021-SGR-623). M.M. thanks the Ministerio de Ciencia, Innovación y Universidades for her fellowship (PID2021 127423NB-I00)

Open Access funding provided thanks to the CRUE-CSIC agreement with American Chemical Society (ACS)