Yields from catalyst-free synthesis of benzo-1,5-diazepines^a.

Product	R1	R2	R3	Yield% A	Yield% B
14a	H	H	CH3	83	72
14b	H	H	CH2CH3	79	68
14c	H	H	t-Bu	75	62
14d	NO2	H	CH3	92	—
14e	NO2	H	CH2CH3	85	—
14f	NO2	H	t-Bu	80	—
14g	Cl	Cl	CH3	83	71
14h	Cl	Cl	CH2CH3	76	64
14i	Cl	Cl	t-Bu	75	66
14j	CH3	CH3	CH3	62	60

^aReaction conditions: o-phenylenediamine 1 (1 eq.) or benzimidazole derivative 6 (1 eq.) and acetylenedicarboxylate 7 (1 eq.) were refluxed in ethanol (30 ml) for 12 h.