Iridium(III)-Catalyzed Tandem Annulation of Pyridine-Substituted Anilines and α-Cl Ketones for Obtaining 2-Arylindoles.

A facile and expeditious protocol for the synthesis of 2-arylindole compounds from readily available N-(2-pyridyl)anilines and commercially available α-Cl ketones through iridium-catalyzed C-H activation and cyclization is reported here. As a complementary approach to the conventional strategies for indole synthesis, the transformation exhibits powerful reactivity, tolerates a large number of functional groups, and proceeds with good to excellent yields under mild conditions, providing a straightforward method to obtain structurally diverse and valuable indole scaffolds. Furthermore, the reaction could be easily scaled up to gram scale.

Rhodium-catalyzed tandem acylmethylation/annulation of N-nitrosoanilines with sulfoxonium ylides for the synthesis of substituted indazole N-oxides.

An atom-economical protocol for synthesizing indazole N-oxides from readily available N-nitrosoanilines and sulfoxonium ylides through the rhodium(iii)-catalyzed C-H activation and cyclization reaction is described here. This protocol employs nitroso as a traceless directing group. The transformation features powerful reactivity, tolerates various functional groups, and proceeds with moderate to good yields under an ambient atmosphere, providing a straightforward approach to access structurally diverse and valuable indazole N-oxide derivatives. Importantly, this new annulation process represents a hitherto unobserved reactivity pattern for the N-nitroso group.

Base-promoted Lewis acid catalyzed synthesis of quinazoline derivatives.

A one-pot protocol has been developed for the synthesis of quinazolinones from amide-oxazolines with TsCl via a cyclic 1,3-azaoxonium intermediate and 6π electron cyclization in the presence of a Lewis acid and base. The process is operationally simple and has a broad substrate scope. This method provides a unique strategy for the construction of quinazolinones.

Ruthenium-catalyzed synthesis of indole derivatives from N-aryl-2-aminopyridines and alpha-carbonyl sulfoxonium ylides.

Indole is a ubiquitous structural motif with important applications in many areas of chemistry. Given this, a simple and efficient Ru(ii)-catalyzed synthesis of indole via intermolecular annulation of N-aryl-2-aminopyridines and sulfoxonium ylides was proposed and accomplished. Excellent selectivity and good functional group tolerance of this transformation were observed. This protocol provides easy access to a wide variety of useful indoles in the presence of a commercially available [Ru(p-cymene)Cl2]2 catalyst. A possible mechanism for the reaction pathway was also proposed. More importantly, this reaction will offer a useful method for the construction of enantioenriched indole frameworks.

Oxidative Recyclization of 1H-Indoles for Synthesis of 2-Indolylbenzoxazinones via Cleavage of the C2-C3 Bond with AIBN under Air.

A novel and concise method for the oxidation of unprotected indole derivatives to synthesize 2-indolylbenzoxazinones in the presence of AIBN under open air has been successfully demonstrated. This metal-free reaction is both atom- and step-efficient and is applicable to a broad scope of substrates. This new methodology provides a facile pathway for oxidative C2-C3 bond cleavage and recyclization of 1H-indoles.