DOUBLE-BOND MIGRATION, CYCLOHEXADIENE DISPROPORTIONATION AND ALKYNE HYDRATION BY DOWEX(R) 1-RHCL3, ION-PAIR CATALYSTS

Polystyrene-supported ion pairs, generated from RhCl3 and Dowex(R) 1 a nion exchangers were shown to be efficient, leach-proof and recyclable catalysts for double bond migration in allylic compounds, disproporti onation of 1,3-cyclohexadiene and hydration of aromatic acetylenes. At 50-70 degrees C the isomerization of allylbenzene in aqueous EtOH was found to be first order in the substrate, and for catalyst:substrate ratio > 1:40, pseudo-zero order in the catalyst. The reaction rate pro ved to be effected by the electronic nature of the allylic compound an d by the structural properties of the polymeric support. The dispropor tionation of the diene in aqueous THF was found to follow the Michaeli s-Menten rate equation. Addition of water was shown to be specific for aromatic alkynes. Aliphatic acetylenes proved to undergo, under the s ame conditions, catalytic oligomerization. While the rate of allylbenz ene isomerization is mainly chemically controlled the disproportionati on of 1,3-cyclohexadiene is governed chiefly by mass transfer processe s. (C) 1997 Elsevier Science B.V.