Gold(III) iminophosphorane complexes as catalysts in C-C and C-O bond formations

The reaction of K[AuCl4] with AgClO4 and iminophosphorane ligands (N, N-IM) Ph3P=NR [R = CH2-2-NC5H4 (1), C(O)-2-NC5H4 (2)] or Ph2PyP=NR [Py = -2-NC5H4; R = Ph (3), C(O) Ph (4)] (mol ratio 1:2.2:1) in acetonitrile affords complexes [AuCl2(N,N-IM)] ClO4 (5-8). These compounds are air- and moisture-stable and they have been evaluated in two types of catalytic processes. They have been found to be effective catalysts in the addition of 2-methylfuran or azulene to methyl vinyl ketone, as well as in the synthesis of 2,5-disubstituted oxazoles from N-propargylcarboxamides. The reactions proceed in mild conditions and with similar yields to those described for AuCl3. Using this method, oxazoles bearing a thiophene functional group 2-(2'-thienyl)-5-methylthiazole can be prepared in excellent yields. In all cases the intermediate 5-methylene-4,5-dihydroxazole can be observed by H-1 NMR. (C) 2008 Elsevier B.V. All rights reserved.