Abstract:
A catalyst useful for the condensation of an aldehyde or ketone starting material with a phenol is an insoluble mercaptosulfonic acid compound. The heterogeneous catalysts comprise catalytically-active species represented by formula (a). L is an optional linking group and is a bond, which catalytically active species is attached by the bond to an insoluble organic or inorganic support; or a catalytically-active species represented by formula (b), wherein L' is an optional linking group, is a bond and theta ' and theta '' are residues of theta , and a and b are independently selected from integers equal to or greater than 1.