Direct access to benzo-fused nine-membered heterocyclic alkenes with a trifluoromethyl carbinol moiety was achieved via a palladium-catalysis.

A highly diastereoselective synthesis of trifluoromethyl-substituted indolines under palladium catalysis is disclosed. The reaction proceeds by interceptive decarboxylative benzylic cycloaddition (IDBC) of nonvinyl, trifluoromethyl benzoxazinanones with sulfur ylides. The palladium-π-benzyl zwitterionic intermediates are suggested for this transformation, and this would be the first example of an IDBC reaction.

The synthesis of pyrazole triflones containing a triflyl group at the 3-position is disclosed. Treatment of 2-diazo-1-phenyl-2-((trifluoromethyl)sulfonyl)ethan-1-one with nitroalkenes under basic conditions gave pharmaceutically attractive pyrazole 3-triflones in good to high yields. The generation of anionic triflyldiazomethane species followed by the [3 + 2] cycloaddition reaction with nitroalkenes is proposed for this transformation. 3-(Difluoromethanesulfonyl)pyrazoles were also synthesized by using a previously unknown anionic (difluoromethanesulfonyl)diazomethane species under a similar strategy.

Substituted and stereochemically dense carbacycles can be prepared by sequential dipolar cycloaddition and reductive cleavage from enals and hydroxylamines. The reaction sequence proceeds with high efficiency for a wide variety of enals and hydroxylamines. The reaction is regio- and diastereoselective for the initial formation of a bridged bisisoxazolidine intermediate, which then undergoes quantitative double N–O cleavage to produce carbacycles as single diastereomers.

Herein we report the first redox-neutral visible-light photocatalytic intermolecular dipolar cycloaddition for the diastereoselective synthesis of isoxazolidines. We have found that vinyl nitrones with a diverse substitution pattern undergo visiblelight-promoted cycloadditions with conjugated carbonyls in the presence of catalytic amounts of Ru(bpy) 3 Cl 2 , with the reaction proceeding with high yields and good selectivities. A redoxneutral pathway is proposed as the primary photoredox mechanism for this transformation.