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Visible Light-Induced [2+2+1] Cycloaddition of 1,6-Enones with α-Bromocarbonyls
Yi Liu1, Weiwei Jin2, Tianqin Zeng1
1Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Materials Science, Zhejiang Normal University, Jinhua 321004, China.
Abstract:
A visible light-induced dehydrobrominative [2+2+1] cycloaddition of 1,6-enones with α-carbonyl alkyl bromides as the one-carbon synthon is accomplished, providing facile and direct access to cis-hexahydro-2H-cyclopenta[b]furans in promising yields with excellent diastereoselectivity. Mechanistic studies indicate a radical cascade featuring the radical addition to C═O bonds, polarity-mismatched 1,5-hydrogen atom transfer of alkoxy radicals, bromination, and an uncommon SN2 cyclization at the quaternary carbon center, thus significantly extending the boundary of the existing [2+2+1] cycloaddition methodology.
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