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Asymmetric synthesis of α-chiral β-hydroxy allenes: copper-catalyzed γ-selective borylative coupling of vinyl arenes and propargyl phosphates†
Jung Tae Han,Jaesook Yun
Chemical Communications Pub Date : 07/24/2019 00:00:00 , DOI:10.1039/C9CC04165F
Abstract

Copper-catalyzed enantioselective coupling of vinyl arenes with bis(pinacolato)diboron (B2pin2) and propargylic phosphates is presented. The protocol affords a facile route to enantioenriched α-branched allenes with a versatile pinacolboronate group at the β-position with high enantioselectivity up to 98 : 2 er. In the presence of a copper catalyst complexed with a chiral bisphosphine ligand, catalytic assembly of α-chiral β-hydroxy allenes was accomplished through highly selective γ-addition of a borylalkyl copper species to propargyl substrates, followed by oxidation. Catalyst-controlled divergent cyclization reactions of the resulting allenes led to concise syntheses of enantioenriched dihydropyran and dihydrofuran rings without any loss of chiral purity.

Graphical abstract: Asymmetric synthesis of α-chiral β-hydroxy allenes: copper-catalyzed γ-selective borylative coupling of vinyl arenes and propargyl phosphates
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