A Route to 5,5-Dithiospiroketals and to Long-Chain Monomers from the Biomass

5,5-Dithiospiroketals are prepared by a double radical addition of α,α′-bisxanthyl acetone to an alkene followed by ionic or thermal cleavage of the xanthate groups and acid-catalyzed ring closure. A modification employs α-chloro-α′-xanthyl acetone to give unsymmetrical derivatives. Reductive removal of the sulfur atoms with Raney nickel furnishes long-chain α,ω-diacids, diols, and diamines. Using biosourced alkenes, monomers and polymers can be obtained where essentially all the carbons are derived from the biomass.