Pd(ii)-catalyzed cycloisomerisation of γ-alkynoic acids and one-pot tandem cycloisomerisation/CuAAC reactions in water†
Joaquín García-Álvarez,Josefina Díez,Cristian Vidal
Green Chemistry Pub Date : 09/07/2012 00:00:00 , DOI:10.1039/C2GC36176K
Abstract

Cycloisomerisation reactions of γ-alkynoic acids into cyclic enol-lactones can be conveniently performed in pure water as a solvent and under aerobic conditions by using a novel iminophosphorane–Pd(II) complex trans-[PdCl22-N,S-(PTA)[double bond, length as m-dash]NP([double bond, length as m-dash]S)(OEt)2}]2 as a catalyst. It is important to note that the catalytic system could be recycled up to 10 consecutive runs. In addition and for the first time, a one-pot tandem orthogonal reaction involving the fast cycloisomerisation of γ-alkynoic acids, followed by an intermolecular atom economical process, i.e. the 1,3-dipolar cycloaddition of azides with terminal alkynes (CuAAC), is reported. This new tandem cycloisomerisation/click reaction proceeds also in water, at room temperature and under aerobic conditions, giving rise to unprecedented bicyclic triazol-enol-lactones under the principles of the so called “Green Chemistry”.

Graphical abstract: Pd(ii)-catalyzed cycloisomerisation of γ-alkynoic acids and one-pot tandem cycloisomerisation/CuAAC reactions in water