Ck. Ghosh et al., BENZOPYRANS .35. REACTION OF 4-OXO-4H-1-BENZOPYRAN-3-CARBOXYLIC ACID AND ITS METHYL-ESTER WITH DIAZOMETHANE, Indian journal of chemistry. Sect. B: organic chemistry, including medical chemistry, 35(7), 1996, pp. 669-672
The title acid 2 on treatment with diazomethane gives furobenzopyran 5
cyclopropane 8 and the pyrazoles 11-13 whereas methyl 4-oxo-4H-1-bent
opyran-3-carboxylate (1) gives its 2-methyl homologue and 8. Compound
8 on heating with methanol yields benzoxepin 9.