Optimisation of reaction conditions for the synthesis of 5-benzyl-3-phenylaminopyrazolo[3,4-d]pyrimidin-4-one (4a) under microwave irradiation^a.

Entry	Solvent	Temp (°C)	Reaction time (min)	Yieldb (%)
1	Toluene	160	35	10
2	MeCN	160	35	66
3	EtOH	160	35	72
4	n PrOH	160	35	35
5	i PrOH	160	35	53
6	Eucalyptol	160	35	28
7	2-MeTHF	160	35	12
8	EtOH	160	45	75
9	EtOH	160	55	83
10	EtOH	160	65	75
11	EtOH	150	55	45
12c	EtOH	Reflux	4320	Tracesd
13e	EtOH	160	55	27

^aThe reactions were performed in a Discover SP (CEM, USA) using 3a (1 mmol), trimethyl orthoformate (3 mmol), and benzylamine (3 mmol) in 2 mL of a solvent under a maximal microwave irradiation power of 150 W.

^bIsolated yield calculated on the basis of 3a.

^cThe reaction was performed using conventional heating under reflux.

^dThe traces are identified in the ¹H NMR spectrum of the crude reaction mixture.

^eThe reaction was performed using conventional heating in a Monowave 50 (Anton Paar, Austria).