HOMOGENEOUS AND BIPHASIC OLIGOMERIZATION OF TERMINAL ALKYNES BY SOME WATER-SOLUBLE RHODIUM CATALYSTS

The catalytic activity of six water soluble rhodium compounds, RhCl3.3 H2O 1, RhCl(Ph2PC6H4-3-SO3Na)3.4H2O2, (COD)RhCl(Ph2PC6H4-3-SO3Na)-H2O3 , [(COD)Rh(mu-Ph2PC6H4-3-SO2-O)]2 4, [(CO)Rh(Ph2PC6H4-3-CO2H)(mu-SPh)] 2 5, and [Rh3O(OAc)6-(H2O)3]OAc 6, for oligomerization of model hydrop hilic and lipophilic terminal alkynes was investigated under homogeneo us and under biphasic conditions. While propynoic acid 7 is converted by all six catalysts solely into trimellitic acid, 8, and trimesic aci d, 9, phenylacetylenes 10 either dimerize, trimerize or give stereoreg ular polymers. The nature of the oligomerization products proved to de pend on the catalyst, the medium and the reaction temperature. In acet onitrile, complex 4 transforms the various phenylacetylenes (except 4- nitrophenylacetylene, 10f ) mainly or entirely to the head-to-tail dim ers, 13, which undergo thermal rearrangement to the head-to-head isome rs, 14.