POLYDENTATE SNXM (X=S,O,N) LIGANDS BY SELECTIVE REDUCTION OF ORGANOSULFUR HETEROCYCLES WITH TRIBUTYLTIN HYDRIDE

Acyclic tetradentate organosulfur ligands of the type S2X2 (where X = S,O,N) can be efficiently prepared by selective desulfurization of bis (1,3-dithiolanes) and bis(1,3-dithianes); bis(1,3-oxathiolanes); and b is(thiazolidines) with two equivalents of tri-n-butyltin hydride. This is a very versatile procedure as many dialdehydes and diketones (or t heir synthetic equivalents) are available for elaboration into bis(thi oheterocycles) by reaction with 1,2-ethane- and 1,3-propanedithiols, m ercaptoethanol or mercaptoethylamine, and their varied structural feat ures can be incorporated into S2X2 ligands. The net result of the proc edure is the controlled formal monoalkylation of dithiols to form comp ounds 1 (X = S); and the alkylation of the less nucleophilic heteroato m (O or N) of mercaptoethanol or mercaptoethylamine to form 1 (X = O,N ).