Dirhodium(ii)-catalysed cycloisomerization of azaenyne: rapid assembly of centrally and axially chiral isoindazole frameworks.

Described herein is a dirhodium(ii)-catalyzed asymmetric cycloisomerization reaction of azaenyne through a cap-tether synergistic modulation strategy, which represents the first catalytic asymmetric cycloisomerization of azaenyne. This reaction is highly challenging because of its inherent strong background reaction leading to racemate formation and the high capability of coordination of the nitrogen atom resulting in catalyst deactivation. Varieties of centrally chiral isoindazole derivatives could be prepared in up to 99 : 1 d.r., 99 : 1 er and 99% yield and diverse enantiomerically enriched atropisomers bearing two five-membered heteroaryls have been accessed by using an oxidative central-to-axial chirality transfer strategy. The tethered nitrogen atom incorporated into the starting materials enabled easy late-modifications of the centrally and axially chiral products via C-H functionalizations, which further demonstrated the appealing synthetic utilities of this powerful asymmetric cyclization.

Catalyst-free synthesis of isoxazolidine from nitrosoarene and haloalkyne via a 1,2-halo-migration/[3 + 2] cycloaddition cascade.

An unprecedented catalyst-free three-component reaction to synthesize isoxazolidine from easily accessible haloalkyne, nitrosoarene and maleimide was developed. This reaction was proposed to proceed via a 1,2-halo migration and [3 + 2] cycloaddition cascade, providing a new reaction pattern of alkyne and nitroso containing species wherein a new type of nitrone was generated. Besides, the reaction conditions were efficient and environmentally benign, enabling the formation of various bioactivity-related isoxazolidines.

Domino Reaction between Nitrosoarenes and Ynenones for Catalyst-Free Preparation of Indanone-Fused Tetrahydroisoxazoles.

A catalyst-free domino reaction to synthesize highly functionalized indanone-fused tetrahydroisoxazole from easily accessed nitrosoarene and 1,6-ynenone with good chemo- and regioselectivity was disclosed. This unprecedented domino reaction represents a new strategy for multifunctionalization of an internal alkyne with nitrosoarene by formation of two rings and four bonds in a single operation.

CuCl/Et3N-Catalyzed Synthesis of Indanone-Fused 2-Methylene Pyrrolidines from Enynals and Propargylamines.

An efficient CuCl/Et3N-catalyzed tandem reaction for the synthesis of indanone-fused pyrrolidine was developed. In this process, two rings and four bonds are generated in one pot with high atom-economy and step-efficiency. The addition of Et3N was found as the key factor for the success of the tandem reaction.