Mechanisms for the synthesis of conjugated enynes from diphenylacetylene and trimethylsilylacetylene catalyzed by a nickel(0) complex: DFT study of ligand-controlled selectivity

Tandem Nickel-Catalyzed Dimerization/(4+2) Cycloaddition of Terminal Alkynes with Four-Membered Ring Ketones

Controlling the behavior of terminal alkynes in metal-catalyzed intermolecular tandem reactions is a formidable challenge despite the potential advantage offered by these strategies in modern synthesis. Herein, we describe that a nickel catalyst enables a tandem process involving the rapid dimerization of terminal alkynes into 1,3-enynes and the cycloaddition of these intermediates with an azetidinone, an oxetanone or benzocyclobutenones. Significantly, the slow or sequential addition of reagents and catalysts is not required to orchestrate their reactivity. These results are in stark contrast with previous cycloadditions of terminal alkynes with strained four-membered ring substrates, which previously led to oligomerization or cyclotrimerization, except in the case of tert-butylacetylene.

Iron-Catalyzed Dehydrative Alkylation of Propargyl Alcohol with Alkyl Peroxides To Form Substituted 1,3-Enynes

This paper reports a new method for the generation of substituted 1,3-enynes, whose synthesis by other methods could be a challenge. The dehydrative decarboxylative cascade coupling reaction of propargyl alcohol with alkyl peroxides is enabled by an iron catalyst and alkylating reagents. Primary, secondary, and tertiary alkyl groups can be introduced into 1,3-enynes, affording various substituted 1,3-enynes in moderate to good yields. Mechanistic studies suggest the involvement of a radical-polar crossover pathway.