Synthesis of various benzazolo[2,1-b]quinazolinones catalyzed by NGPU.^a.

Entry	Ar	R	Product	Time (min)	Yieldb (%)	M.p. (°C)
						Found	Reported
1	C6H5	CH3	1b	29	99	>300	>300 (ref. 28)
2	4-Cl–C6H4	CH3	2b	22	98	>300	>300 (ref. 32)
3	4-Br–C6H4	CH3	3b	33	98	>300	>300 (ref. 32)
4	4-OH–C6H4	CH3	4b	14	99	>300	>300 (ref. 52)
5	2,4-Cl2–C6H3	CH3	5b	27	98	>300	>300 (ref. 32)
6	3,4,5-(OCH3)3–C6H2	CH3	6b	12	95	>300	>300 (ref. 53)
7	4-CH3–C6H4	CH3	7b	13	99	>300	>300 (ref. 32)
8	2-CH3–C6H4	CH3	8b	8	99	>300	>300 (ref. 28)
9	3-NO2–C6H4	CH3	9b	18	85c	>300	>300 (ref. 32)
10	C6H5	H	10b	6	98	>300	310–312 (ref. 54)
11	2-CH3–C6H4	H	11b	15	96	>300	New
12	2-Br–C6H4	H	12b	7	89	>300	New
13	3,4,5-(OCH3)3–C6H2	H	13b	2	99	>300	>300 (ref. 55)
14	4-Pyridinebenzaldehyde	H	14b	18	95	>300	New
15	4-NO2–C6H4	H	15b	20	95	>300	>300 (ref. 54)
16	4-F-C6H4	H	16b	24	90	>300	>300 (ref. 54)

^aReaction conditions: aldehyde (1 mmol), 1,3-diketones (dimedone and/or 1,3-cyclohexanediones) (1 mmol), 2-aminobenzimidazole (1 mmol).

^bIsolated yields.

^cIsolated yields after recrystallization.