Enantioselective Synthesis of Spiroindenes by Enol-Directed Rhodium(III)-Catalyzed C-H Functionalization and Spiroannulation.

Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol-directed C(sp(2))-H functionalization and oxidative annulation with alkynes to give spiroindenes containing all-carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O-bound rhodium enolate into the C-bound isomer, appear to be critical for high enantiomeric excesses.

Catalyst-controlled divergent C-H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds with alkynes and alkenes.

Achieving site-selective, switchable C-H functionalizations of substrates that contain several different types of reactive C-H bonds is an attractive objective to enable the generation of different products from the same starting materials. Herein, we demonstrate the divergent C-H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds that contain two distinct, nonadjacent sites for initial C-H functionalization, where product selectivity is achieved through catalyst control. By use of a palladium-N-heterocyclic carbene complex as the precatalyst, these substrates undergo oxidative annulation with alkynes to provide spiroindenes exclusively. In contrast, a ruthenium-based catalyst system gives benzopyrans as the major products. Examples of divergent, oxidative C-H alkenylations of the same substrates are also provided.

Synthesis of benzopyrans by Pd(II)- or Ru(II)-catalyzed C-H alkenylation of 2-aryl-3-hydroxy-2-cyclohexenones.

2-Aryl-3-hydroxy-2-cyclohexenones are shown to be competent substrates for palladium- and ruthenium-catalyzed C-H alkenylation reactions with terminal alkenes, providing, in most cases, benzopyrans.