A Practical Catalyst-Free Synthesis of 6-Amino-4 Alkyl/Aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-carbonitrile in Aqueous Medium

Table 1

Synthesis of 6-amino-4-aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-carbonitriles via Scheme 1^a.

Entry	Aldehyde	Product^b	Time (h)	% Yield^c	m.p. (°C) [Ref]
1			2	95	195 [4]
2			2	90	191 [4]
3			2	87	222–224 [5]
4			4	80	175 [4]
5			4	78	177 [6]
6			4	76	169 [4]
7			5	80	174 [4]
8			4	90	195 [4]
9			6	70	204–206
10			5	87	223–226 [7]

^aReaction conditions: Stoichiometric ratio of ethyl acetoacetate, hydrazine hydrate, aldehyde, and malononitrile were refluxed in water. ^bThe products were purified by recrystallization from ethanol. ^cYield of the pure product.