N-tert-Butyl-3-(hydrazonomethyl)-5,5-dimethyl-5,6-dihydro-4H-cyclopenta[b]thiophene-2-carboxamide → 7,7-Dimethyl-7,8-dihydro-3H-cyclopenta[4,5]thieno[2,3-d]pyridazin-4(6H)-one

Participants

Reaction Steps

A solution of 131g (3.8 g, 13.0 mmol) in 30% H2SO4 (100 mL) was heated at reflux for 16 h. See FIG. 15. The reaction mixture was cooled to room temperature and extracted with dichloromethane (3×200 mL). The combined organic layer was concentrated under reduced pressure and the residue was purified by silica-gel column chromatography eluting with 100:1 dichloromethane/methanol to afford 131h as a yellow solid (1.72 g, 60%). MS-ESI: [M+H]+ 221.0

Provenance & Evidence