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 2

Synthesis of 6-amino-4-alkyl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-carbonitriles^a.

Entry	Aldehyde	Product^b	Time (h)	% Yield^c	m.p. (°C) [Ref]
1			10	70	131–133 [14]
2			10	74	146–148 [6]
3			10	78	150–153 [16]
4			10	80	153–154
5			3	80	190–192
6	EtO2CCHO		6	84	187–189

^aReaction conditions: Stoichiometric ratio of ethyl acetoacetate, hydrazine hydrate, aldehyde, and malononitrile were refluxed at 100°C in 1 : 1 water-ethanol mixture. ^bThe products were purified by recrystallization from ethanol. ^cYield of the pure product.