Table 2.

The relative energies (kJ/mol) of four tautomers of bicyclic compounds 12–17 (Figure 2) calculated at the B3LYP/6-311++G(2df,2pd) level.

	2,3-I (keto)	1,2-I (keto)	2,4-I (enol)	1,3-I (imino) 1
12	0.0	41.0	33.8	49.0
13	0.0	17.2	34.3	32.6
14	0.0	38.5	38.3	45.1
15	0.0	11.5	48.7	27.3
16	0.0	8.5	46.8	20.1
17	0.0	10.8	30.6	21.0

¹ The energies of both rotamers of the imino group have been calculated, the lower of which is presented here. The energies of both rotamers are given in the SI.