Solvent-Free Green and Efficient One-Pot Synthesis of Dihydropyrano[3,2-c]chromene Derivatives

Table 2

Synthesis of 2-Amino-4-aryl-3-cyano-5-oxo-4H,5H-pyrano[3,2-c]chromenes in solvent-free neat conditions using DABCO (5 mol%) as catalyst.

Entry	Ar	Product	Time/min	Yield/%	m.p./°C Found (reported)
1	C6H5	4a	30	94	256-257 (256–258) [15]
2	4-O2N C6H4	4b	30	96	259–261 (258–260) [15]
3	3-O2N C6H4	4c	30	93	261–263 (262–264) [15]
4	4-ClC6H4	4d	30	92	264–267 (263–265) [15]
5	4-BrC6H4	4e	30	91	247–250 (249–251) [15]
6	4-CH3OC6H4	4f	30	89	241–244 (240–242) [15]
7	4-CH3C6H4	4g	30	87	252–254 (250–252) [15]
8	2,4-Cl2C6H3	4h	30	90	256–258 (257–259) [15]
9		4i	30	97	251–254 (252-253) [16]
10		4j	30	96	226–230 (228) [20]