A synthetic method for highly substituted pyridinium salts from the multicomponent reaction of vinyl ketones/aldehydes, amines, and alkynes using a rhodium catalyst is demonstrated. The catalytic reaction proceeds via an in situ generated imine-assisted Rh(III)-catalyzed vinylic C-H activation.

A method for the synthesis of substituted quinolizinium salts from 2-ethylpyridines and alkynes is demonstrated. The transformation is conveniently achieved using 1 mol % of a Rh(III) catalyst along with an excess amount of copper(II) salt. The reaction gives high product yields with broad substrate scope and functional group tolerance. Detailed mechanistic studies suggest that 2-vinylpyridine is formed in situ from 2-ethylpyridine by a copperpromoted C(sp 3 )−H hydroxylation, followed by dehydration. Later, a Rh(III)-catalyzed pyridine-directed vinylic C(sp 2 )−H activation and annulation with alkynes provided the final product.

A novel method for the synthesis of substituted quinolines from benzylic azides and internal alkynes using Cu(OTf)2is described. The reaction features a broad substrate scope, high product yields and excellent regioselectivity.

An iron‐catalyzed synthesis of α,β‐unsaturated carboxylic acids from alkynes and carbon dioxide was developed. This reaction proceeds through hydromagnesiation of alkynes followed by carbon dioxide insertion under atmospheric pressure and ambient temperature in the presence of iron and a Grignard reagent as a catalyst and hydride source, respectively. Several symmetrical and unsymmetrical alkynes were transformed into the corresponding acids in good to excellent yields. The methodology provides an efficient route to the synthesis of vinyl carboxylic acids.

Highly substituted pyridinium salts are synthesized via a multicomponent reaction of vinyl ketones/aldehydes, amines, and alkynes.