4-Nitrobenzamide → 5,6-Dihydro-6-hydroxy-5,5-dimethyl-7-(4-nitrobenzamido)-7H-thieno[3,2-b]pyran

Participants

Reaction Steps

6-Bromo-7-hydroxy-5,6-dihydro-5,5-dimethyl-7H-thieno[3,2-b]-pyran (6.8 g, 25.8 mmol) and 4-nitrobenzamide (10.7 g, 64.5 mmol) were treated with sodium hydride 60% in oil (2.26 g, 56.8 mmol) in N,N-dimethylformamide (110 mL) using the procedure described for the preparation of 5,6-dihydro-6-hydroxy-5,5-dimethyl-7-(2-oxopyrrolidin-1-yl)-7H-thieno[3,2-b]pyran. The reaction mixture was poured into water and extracted into 10% isopropanol in dichloromethane. The solvent was evaporated in vacuo and the residue was purified by medium pressure chromatography using 2% methanol in dichloromethane as the eluant to give the product, 4.5 g (50%), as a pale yellow solid: mp 183°-186° C. dec; IR (KBr): 3398, 1664, 1644 and 1601 cm-1 ; MS: m/z 349 (MH+); 1H NMR (CDCl3): δ1.35(s, 3H), 1.50(s, 3H), 3.79(d, J=7.9 Hz, 1H), 4.26(bs, 1H, exchanges with D2O), 5.19(d, d, J=7.9 Hz, and J=7.0 Hz, 1H), 6.59(bd, J=7.0 Hz, 1H, shifts to 6.66 with D2O), 6.63(d, J=5.4 Hz, 1H), 7.18(d, J=5.4 Hz, 1H), 7.97(d, J=8.8 Hz, 2H) and 8.32(d, J=8.8 Hz, 2H).

Provenance & Evidence