Access to Azetidines via Gold Mediated Energy Transfer Photocatalysis

Abstract

The area of energy transfer photocatalysis to generate four-membered rings is experiencing an unprecedented level of activity. Here, we report an operationally simple method toward azetidines from 2-isoxasoline-3-carboxylates and alkenes, using [Au(cbz)(NHC)] complexes as photocatalysts. The procedure enables the reaction for a wide range of substrates. Mechanistic studies confirm the energy transfer pathway. This contribution adds to the earlier reported use of these gold catalysts as a potentially versatile tool in energy transfer chemistry and catalysis.

Synthesis of cyclobutane-fused chromanones via gold-mediated photocatalysis

“…35 Moreover, these gold complexes allowed for a wide range of reactions in commonly-used and environmentally-friendly organic solvents, typically with shorter reaction times than when iridium photocatalysts are used. 35,36 Such features showcase gold sensitizers as attractive alternatives to Ir analogues, which are dominant in the area of EnT catalysis. We now report on a simple protocol to access cyclobutane-fused chromanones via gold-catalyzed energy transfer [2 + 2]-cycloaddition between coumarins and various alkenes.…”

Synthesis of N-heterocyclic carbene (NHC)-Au/Ag/Cu benzotriazolyl complexes and their catalytic activity in propargylamide cycloisomerization and carbonyl hydrosilylation reactions

“…6,7 Recent studies have also revealed them as highly-efficient light-absorbing materials in solar cell applications, with improved performance and cost-effectiveness. 2,[8][9][10][11][12] In the field of medicine, a wide range of CMAs have shown anti-cancer, anti-inflammatory, antiviral, and/or antimicrobial properties, and are being explored for potential use in pharmaceuticals. 13 Recently, the synthesis of a new series of carboline-derived CMAs with potent anticancer activity has also been reported.…”

Synthesis of cyclohepta[b]indoles via gold mediated energy transfer photocatalysis

“…24 With high triplet energy values, namely 67.9 kcal mol −1 for PhotAuCat I and 67.6 kcal mol −1 for PhotAuCat II , these have demonstrated efficiency in diverse [2+2]-photocycloadditions, surpassing state-of-the-art Ir photocatalysts. 25–27…”

“…24 With high triplet energy values, namely 67.9 kcal mol À1 for PhotAuCat I and 67.6 kcal mol À1 for PhotAuCat II, these have demonstrated efficiency in diverse [2+2]-photocycloadditions, surpassing state-of-the-art Ir photocatalysts. [25][26][27] Cyclohepta[b]indole serves as a core unit in some natural products as well as in various pharmaceutical compounds. 28 For example, arcyriacyanin A isolated from Arcyria nutans inhibits protein kinase C and tyrosine kinase and exhibits cytotoxicity against human cancer cells.…”