Deep eutectic solvents: biorenewable reaction media for Au(i)-catalysed cycloisomerisations and one-pot tandem cycloisomerisation/Diels–Alder reactions?

Green Chemistry Pub Date: 2015-05-15 DOI: 10.1039/C5GC00656B

Abstract

Cycloisomerisation reactions of (Z)-enynols into furans can be conveniently performed, for the first time, in the eutectic mixture 1ChCl/2Gly as a solvent and under standard bench conditions (at room temperature and under air) by using the new bis(iminophosphorane)–Au(I) complex [Au2Cl2(μ2-S,S-CH2{P([double bond, length as m-dash]NP([double bond, length as m-dash]S)(OPh)2)Ph2}2)] as a catalyst. Furthermore, a one-pot tandem reaction involving the fast cycloisomerisation of (Z)-enynols followed by an intermolecular atom economical process, i.e. the Diels–Alder reaction with activated alkynes or alkenes, is reported. This tandem cycloisomerisation/Diels–Alder reaction proceeds also in the eutectic mixture 1ChCl/2Gly, in the absence of co-catalysts and under aerobic conditions, giving rise to the corresponding 7-oxanorbornadienes and 7-oxanorbornenes under the principles of the so-called Green Chemistry.

Graphical abstract: Deep eutectic solvents: biorenewable reaction media for Au(i)-catalysed cycloisomerisations and one-pot tandem cycloisomerisation/Diels–Alder reactions
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