2011•Letters in Organic ChemistryRequires access
Facile Regioselective Synthesis of Benzofuran-Annulated Six-Membered Sulfur Heterocycles and the Occurrence of Thermal [1,3] Sigmatropic Rearrangement
Krishna C. Majumdar, Sanjay Nath, Buddhadeb Chattopadhyay, Krishanu Ray
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Abstract
Thio-Claisen rearrangement of a number of 3-(4-aryloxybut-2 – ynlthio)benzofurans has been achieved under very mild conditions to give 2H-benzo[b]thiopyrano[2,3-d]furans. Attempts at further thio-claisen rearrangement resulted in the occurrence of thermal [1s, 3a] sigmatropic shift. Keywords: Thio-Claisen rearrangement, [3,3] sigmatropic rearrangement, sulfur heterocycles, regioselective cyclization, [1,3] hydrogen shift, thiopyrano, thieno[3,2-c]coumarins, methyl, pyranothiopyran, furan