Studies in sigmatropic rearrangement: synthesis of 3,11a-dimethyl-6a,11a-dihydro-1H,6H-pyrano[3',4':5,6]thiopyrano[4,3-b][1]benzofuran-1-one - Majumdar, K. C.; Kundu, U. K.; Mukhopadhyay, P. P.; Ghosh, S. (ARKIVOC, 2004)
doi: 10.3998/ark.5550190.0004.907