Rhodium-Catalyzed Heck-Type Coupling of Boronic Acids with Activated Alkenes in an Aqueous Emulsion

Abstract

Intermolecular couplings between arylboronic acids and activated alkenes catalyzed by a water-soluble tert-butyl amphos-rhodium complex were found to progress at room temperature and generated Heck-type products with high yields and excellent selectivity. Substitution on the alkene component encouraged the formation of products arising from a conjugate addition-protonation process. In the case of Heck product formation, it was necessary to add two equivalents of the alkene component whereby one equivalent is believed to act as a sacrificial hydride acceptor.

Key words

rhodium - Heck reaction - boron - olefination - alkylations

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1

Present address: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA

12

Boronic acids and boronate esters readily undergo transmetalation with this catalyst system; there is no noticeable difference in reactivity.

18

Isolation of saturated addition product was also observed for the reaction of arylsilanediols and methyl vinyl ketone under both aqueous and anhydrous conditions by Mori and coworkers, see ref. [11b]