Table 1.

Yields of products of the reaction of furan-2,3-dione 1a and azirine 2a in boiling benzene solution for 0.5 h according to ¹H NMR.

Ratio 2a:1a	Conversion of 2a (%)	Yieldsa of 3a, 4a, 5a, %	Overall yieldsa of 3a–5a, %
1:2	100	2, 16, 9	27
1:1.5	89	5, 22, 17	44
1:1	42	19, 37, 15	71
1.5:1	57	2, 19, 11	32
2:1	43	4, 20, 13	37

^aYield based on consumed azirine 2a.