Efficient and sustainable tandem annulation-decarboxylation reaction using ecocatalysis

Abstract

Substituted cyclohexenones are well-known building blocks for the synthesis of numerous natural products and bioactive compounds. Despite their widespread use, they are prepared under conditions that are not compatible with the principles of green chemistry. Here the synthesis of substituted cyclohexenones was revisited using a tandem annulation-decarboxylation strategy, in an eco-friendly process without compromising on efficiency. To meet this challenge, environmental catalysts, named ecocatalysts®, which derived from biomass wastes were used. Under microwave activation, ecocatalysis assisted by statistical tools led to excellent yields, as well as remarkable green metrics for the whole synthetic process, which both exceeded those previously reported. The reaction was scaled-up allowing the recycling assessment of the best ecocatalysts®. The reaction was also extended to other substrates. The catalytically active species within the best ecocatalyst® was identified through extensive characterisation by MP-AES, XRPD, SEM, XPS and solid-state NMR, allowing to depict a mechanism confirmed by DFT calculations.