Viable utilization of polycarbonate as a phosgene equivalent illustrated by reactions with alkanedithiols, mercaptoethanol, aminoethanethiol, and aminoethanol: A solution for the issue of carbon resource conservation

Methods for the chemical recycling of polycarbonate (PC) wastes in the forms of bisphenol A (BPA) and cyclic heterocarbonates, such as 1,3-dithiolan-2-one (DTO), 1,3-dithiane-2-one (DTA), and cyclic unsymmetric heterocarbonates, were investigated to prove that PC can be utilized as a phosgene equivalent for industrial purposes. Treatment of PC pellets or waste PC compact discs with 1,2-ethanedithiol and a catalytic amount of base (e.g., 1.5 mol % NaOH) in dioxane for a short period at 40degreesC produced DTO and BPA, both in nearly quantitative yields. The reaction could also be carried out in DTO, which saved the use of conventional solvents. Other cyclic heterocarbonates, that is, DTA, 1,3-oxathiolan-2-one, 1,3-thiazolidine-2-one, and N-methyl-1,3-oxazolidine-2-one, were prepared in high yields under analogous conditions. (C) 2003 Wiley Periodicals, Inc.