Insight into the palladium catalyzed oxidative arylation of benzofuran: Heteropoly acid oxidants evoke a Pd(II)/Pd(IV) mechanism.

The effects of oxidant and organic acid additives on the oxidative cross-coupling reactions of electron rich heterocycles such as benzofuran with benzene were studied. Both regioselectivity and reaction rate could be controlled by varying the condition parameters. Furthermore, mechanistic insight was achieved via kinetic studies which indicate that reactions that are oxidized by the heteropoly acid H4PMo11VO40 operate via a Pd(II)/Pd(IV) mechanisms, while reactions oxidized by either AgOAc or Cu(OAc)2 operate by a Pd(II)/Pd(0) mechanism.

Metal-free intermolecular oxidative C-N bond formation via tandem C-H and N-H bond functionalization.

The development of a novel intermolecular oxidative amination reaction, a synthetic transformation that involves the simultaneous functionalization of both a N-H and C-H bond, is described. The process, which is mediated by an I(III) oxidant and contains no metal catalysts, provides a rapid and green method for synthesizing protected anilines from simple arenes and phthalimide. Mechanistic investigations indicate that the reaction proceeds via nucleophilic attack of the phthalimide on an aromatic radical cation, as opposed to the electrophilic aromatic amination that has been reported for other I(III) amination reactions. The application of this new reaction to the synthesis of a variety of substituted aniline derivatives is demonstrated.

Increasing synthetic efficiency via direct C-H functionalization: formal synthesis of an inhibitor of botulinum neurotoxin.

A new and efficient scheme for the synthesis of one of the best known inhibitors of botulinum neurotoxin serotype A (BoNTA) is reported herein. The synthetic route involves two palladium-catalyzed C-H functionalization reactions, formally activating three C-H bonds.

Regioselective oxidative arylation of indoles bearing N-alkyl protecting groups: dual C-H functionalization via a concerted metalation-deprotonation mechanism.

The most direct method for synthesizing 2-arylindoles is oxidative coupling of an arene with an indole. We have shown that both the activity and regioselectivity of this cross-coupling reaction are correlated with the acidity of the medium. This insight has been applied to predict the best conditions for the oxidative cross-coupling of N-alkylindoles, an important class of substrates that has heretofore been incompatible with the harsh conditions required for oxidative cross-coupling. Both experimental and computational data indicate that the mechanism for C-H palladation of both the indoles and simple arenes is best described as concerted metalation-deprotonation, regardless of the substitution on the arene.

Oxidant-controlled regioselectivity in the oxidative arylation of N-acetylindoles.

N-Acetylindoles can be oxidatively coupled with arenes such as benzene or pentafluorobenzene in dioxane. The use of Cu(OAc)(2) as the stoichiometric oxidant produces selective arylation at the 3-position of indole while AgOAc produces selective arylation at indole's 2-position.