An unusual reaction of Lawesson's reagent with 1,8-diketones: A synthesis of fused 1,4-dithiins and thiophenes

Article abstract of DOI:10.1016/0040-4039(96)00396-6

Reaction of 1,8-diketones 3 with Lawesson's reagent 8 resulted in the formation of five and six-membered rings 5-7, 18, depending on the nature of the substituents. Product 6 is converted in two steps to the unsymmetric 'ET' analogue 20, containing an extra double bond.