A Convenient C-H Functionalization Platform for Pyrroloiminoquinone Alkaloid Synthesis.

Pyrroloiminoquinone alkaloids represent a structurally intriguing class of natural products that display an array of useful biological properties. Here, we present a versatile and scalable platform for the synthesis of this diverse family - and in particular the antitumor discorhabdins - built upon sequential selective C-H functionalization of tryptamine. The utility of this strategy is showcased through short formal syntheses of damirones A-C, makaluvamines D and I, and discorhadbin E.

Stereoselective Synthesis of Tetrasubstituted Alkenes via a Cp*Co -Catalyzed C-H Alkenylation/Directing Group Migration Sequence.

A highly atom economical and stereoselective synthesis of tetrasubstituted α,β-unsaturated amides was achieved by a Cp*Co -catalyzed C-H alkenylation/directing group migration sequence. A carbamoyl directing group, which is typically removed after C-H functionalization, worked as an internal acylating agent and migrated onto the alkene moiety of the product. The directing group migration was realized with the Cp*Co catalyst, while a related Cp*Rh catalyst did not promote the migration process.

Site- and Regioselective Monoalkenylation of Pyrroles with Alkynes via Cp*Co Catalysis.

A site-, regio-, syn-, and monoselective alkenylation of dimethylcarbamoyl-protected pyrroles proceeded using a catalytic amount of [Cp*Co(CHCN)](SbF) and KOAc. A variety of internal alkynes with several functional groups and a terminal alkyne afforded hydropyrrolation products in a selective manner in good to excellent yield. The site-selectivity (C2/C5 selectivity) observed for C3-substituted pyrroles is noteworthy because Cp*Rh-catalyzed conditions afforded only a moderate yield and low selectivity.

Pyrroloindolone synthesis via a Cp*Co(III)-catalyzed redox-neutral directed C-H alkenylation/annulation sequence.

A unique synthetic utility of a Cp*Co(III) catalyst in comparison with related Cp*Rh(III) catalysts is described. A C2-selective indole alkenylation/annulation sequence proceeded smoothly with catalytic amount of a [Cp*Co(III)(C6H6)](PF6)2 complex and KOAc. Intramolecular addition of an alkenyl-Cp*Co species to a carbamoyl moiety gave pyrroloindolones in 58-89% yield in one pot.