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

Table 1

DABCO catalyzed synthesis of 4a in different reaction conditions.

Entry	Solvent	𝑇/°C	Time/h	Yield^a/%
1	EtOH	Reflux	2	85
2	CH2Cl2	Reflux	6	54
3	CH3CN	Reflux	4	73
4	THF	Reflux	4	62
5	H2O	Reflux	1.5	87
6	—	100	0.5	94
7	—	60	2	65
8	—	80	1	76
9	—	120	0.5	92
10^b	—	100	2	65
11^c	—	100	0.5	95

aIsolated yield.
^b1 mol% of catalyst was used.
^c10 mol% of catalyst was used.