Gold-catalyzed highly regioselective oxidation of C-C triple bonds without acid additives: propargyl moieties as masked α,β-unsaturated carbonyls

Gold-catalyzed intermolecular oxidations of internal alkynes have been achieved with high regioselectivities using 8-alkylquinoline N-oxides as oxidants and in the absence of acid additives. Synthetically versatile α,β-unsaturated carbonyls are obtained in good to excellent yields and with excellent E-selectivities. A range of functional groups such as THP, MOMO, N(3), OTBS, and N-Boc are tolerated. This reaction allows α,β-unsaturated carbonyls to be masked as propargyl moieties, thus offering a practical solution to compatibility issues with these functional groups likely encountered in syntheses of complex structures.

Site-specific introduction of gold-carbenoids by intermolecular oxidation of ynamides or ynol ethers

Ynamides and ynol ethers undergo intermolecular gold-catalysed reaction with a nucleophilic oxidant to access metal-carbenoid reactivity patterns. A site-specific oxidation/1,2-insertion cascade is used for a general access to functionalised α,β-unsaturated carboxylic acid derivatives and vinylogous carbimates.

Gold(I)-catalysed alcohol additions to cyclopropenes

Gold(i)-catalysed addition of alcohols to 3,3-disubstituted cyclopropenes occurs in a highly regioselective and facile manner to produce alkyl tert-allylic ethers in good yields. The reaction is tolerant of sterically hindered substituents on the cyclopropene as well as primary and secondary alcohols as nucleophiles. In this full article, we report on the substrate scope and plausible mechanism, as well as the regioselectivity issues arising from subsequent gold(i)-catalysed isomerisation of tertiary to primary allylic ethers.

Alkynes as equivalents of alpha-diazo ketones in generating alpha-oxo metal carbenes: a gold-catalyzed expedient synthesis of dihydrofuran-3-ones

An expedient and reliable method for accessing reactive alpha-oxo gold carbenes via gold-catalyzed intermolecular oxidation of terminal alkynes has been developed. Significantly, this method offers a safe and economical alternative to the strategies based on diazo substrates. Its synthetic potential is demonstrated by expedient preparation of dihydrofuran-3-ones containing a broad range of functional groups.