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Palladium(II)-Catalyzed Directed anti-Hydrochlorination of Unactivated Alkynes with HCl
Joseph Derosa1, Annabelle L Cantu1, Mark N Boulous1
1Department of Chemistry, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States.
Abstract:
A regioselective anti-hydrochlorination of unactivated alkynes is reported. The reaction utilizes in situ generated HCl as the source of both the Cl- and H+ and is catalyzed by palladium(II) acetate, with loadings as low as 25 ppm. Removable picolinamide and 8-aminoquinoline bidentate directing groups are used to control the regioselectivity of the chloropalladation step and stabilize the resulting alkenylpalladium(II) intermediate for subsequent protodepalladation. This method provides access to a broad array of substituted alkenyl chlorides in excellent yields and with high regioselectivity. The products from this transformation were successfully derivatized via Stille coupling to a variety of trisubstituted alkene products. Reaction progress kinetic analysis was performed, shedding light on a possible mechanism for this catalytic process.
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