α‐Aminoazoles in Syntheses of Heterocycles. 3(5)‐Aminopyrazole‐4‐carbonitriles in the Synthesis of Pyrazolo[1,5‐a]pyrimidines.

Abstract

Fused pyrimidine derivatives R 0515 α-Aminoazoles in Syntheses of Heterocycles. 3(5)-Aminopyrazole-4-carbonitriles in the Synthesis of Pyrazolo[1,5-a]pyrimidines. -A procedure for the regioselective synthesis of substituted 7-aryl-5-methylpyrazolo[1,5-a]pyrimidines (III) that are structurally related to the sedative and soporitic drug Zaleplon is described. -(EMELINA, E. E.; PETROV, A. A.; FIRSOV, A. V.; Russ. J. Org. Chem. 43 (2007) 3, 471-473; St. Petersburg State Univ., St. Petersburg 198504, Russia; Eng.) -D. Singer 36-147

Synthesis of 5-Substituted 3-Amino-1H-Pyrazole-4-Carbonitriles as Precursors for Microwave Assisted Regiospecific Syntheses of Pyrazolo[1,5-a]Pyrimidines

“…Reactions of unsymmetrical 1,3-diketones with 3(5)-aminopyrazoles often lead to the formation of inseparable mixtures of two regioisomeric pyrazolo[1,5- a ]pyrimidines due to comparable reactivity’s of the two electrophilic centers in the initial diketone. Recently, use of 1,3-dimethyluracil as the electrophile was reported to involve the attack on both endocyclic and exocyclic nitrogen affording either the pyrazolo[1,5- a ]pyrimidin-5-one or 7-one isomers, depending on the reaction conditions [ 15 ], whereas the reaction of 1 H -3-aminopyrazole with benzylidenemalononitrile [ 16 ] and with 1-arylbutane-1,3-diones [ 17 ] are established to involve exocyclic amino group. It is thought that there is an equilibrium between possible initial attack at the ring nitrogen and the exocyclic amino group.…”