[3+3] Annulation of donor-acceptor cyclopropanes with mercaptoacetaldehyde: application to the synthesis of tetrasubstituted thiophenesElectronic supplementary information (ESI) available: Experimental procedures and characterization data for all products, including copies of 1H and 13C NMR spectra and X-ray structural information of 3m and 4d (CIF). CCDC 981071 and 981072. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4cc00565a

A conceptually new method for synthesis of tetrasubstituted thiophenes in two steps from trans -2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol has been developed. It involves AlCl 3 -mediated [3+3] annulation of the cyclopropane-derived 1,3-zwitterionic intermediates with in situ generated mercaptoacetaldehyde, followed by DBU-induced rearrangement of the resulting tetrahydrothiopyranols. The target thiophenes are produced in 55-82% yields. A de novo synthesis of tetrasubstituted thiophenes in two steps from trans -2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol is described.