Metal- and Photocatalysis To Gain Regiocontrol and Stereodivergence in Hydroarylations of Unsymmetrical Dialkyl Alkynes

Abstract

We report on a regioselective, stereodivergent catalytic hydroarylation of unsymmetrical dialkyl alkynes with arylboronic acids that allows highly selective access to either the E or Z diastereoisomer of trisubstituted alkenes. The E selectivity is achieved through syn-carbopalladation of the alkyne by Ar–Pd species followed by protodepalladation in which a 2-pyridyl sulfonyl (SO2Py) directing group enables complete control of the regioselectivity. Access to the complementary stereochemistry is achieved through a tandem Pd/Ir sequence, which includes hydroarylation and E→Z photoisomerization. Finally, facile removal of the directing group by reduction, Julia–Kocienski olefination, or Cu-catalyzed C(sp3)–C(sp2) or C(sp3)–C(sp3) cross coupling allows for the selective preparation of stereodefined olefins and dienes.