Efficient synthesis of 2-amino-4-aryl-8-[(E)-arylmethylidene]-5, 6, 7, 8-4H pyrano [3, 2-c]pyridine in green media

Figures & data

Scheme 1.  Synthesis of 2-amino-4-aryl-8[(E)-arylmethylidene]-5,6,7,8,-4H pyrano[3,2-c] pyridine 3a-f in green media.

Table 1. Synthesis of tetrahydro-4H-pyrano [3,2-c]pyridines in aqueous media

Entry	Ar	Catalyst^a	Time (h)	Yield (%)^b
3a	C6H5	(NH4)2HPO4	4	87
		Piperidine	4	85
3b	C4H3S	(NH4)2HPO4	3	86
		Piperidine	4.5	86
3c	4-Cl–C6H4	(NH4)2HPO4	4	85
		Piperidine	4	83
3d	Me2N–C6H4	(NH4)2HPO4	4	79
		Piperidine	3.5	78
3e	3-O2N–C6H4	(NH4)2HPO4	4	95
		Piperidine	4	93
3f	4-O2N–C6H4	(NH4)2HPO4	3	96
		Piperidine	4	96
^aIn all cases the catalysts were used 10% equiv.
^bIsolated yields