BIFUNCTIONAL CHIRAL AUXILIARIES .5. THE SYNTHESIS OF 1,3-DIACYLIMIDAZOLIDINE-2-THIONES AND 1,3-DIACYLIMIDAZOLIDIN-2-ONES FROM 1,2-DIAMINES

Although 1,2-diamines fail to cyclise with urea, phosgene or 1,1'-carb onyl diimidazole, they react with carbon disulphide to give the corres ponding imidazolidine-2-thiones. These undergo clean diacylation to gi ve 1,3-diacylimidazolidine-2-thiones which are readily converted to 1, 3-diacylimidazolidin-2-ones on treatment with mercury (II) acetate. An alternative two-step route to 1,3-diacylimidazolidin-2-ones uses carb onyl sulphide to effect cyclisation of the 1,2-diamine to the imidazol idin-2-one, which is subsequently diacylated. The ability to convert h omochiral 1,2-diamines to homochiral 1,3-diacylimidazolidin-2-ones has also been demonstrated.