Benzyl 5-phenylpyrazolo[5,1-a]isoquinoline-1-carboxylate

In the title compound, C25H18N2O2, the pyrazolo[5,1-a]isoquinoline ring system is approximately planar [maximum deviation = 0.027 (2) Å] and is oriented at dihedral angles of 57.22 (6) and 71.36 (7)° with respect to the two phenyl rings. The phenyl rings are twisted to each other by a dihedral angle of 66.33 (8)°. A weak intramolecular C—H⋯O hydrogen bond occurs. In the crystal, weak C—H⋯π interactions are present.

In the title compound, C 25 H 18 N 2 O 2 , the pyrazolo[5,1-a]isoquinoline ring system is approximately planar [maximum deviation = 0.027 (2) Å ] and is oriented at dihedral angles of 57.22 (6) and 71.36 (7) with respect to the two phenyl rings. The phenyl rings are twisted to each other by a dihedral angle of 66.33 (8) . A weak intramolecular C-HÁ Á ÁO hydrogen bond occurs. In the crystal, weak C-HÁ Á Á interactions are present.

Comment
In the last decade, diversity-oriented synthesis has been widely used to efficiently generate diverse small molecules. Among the strategies employed in diversity-oriented chemical synthesis, multi-component reactions are very attractive processes that push the limits of synthetic efficiency by using more than two reactants to create novel products with an optimal number of new bonds and functionalities (Dömling & Ugi, 2000;Nair et al., 2003;Ramon & Yus, 2005). Among the family of isoquinolines, the fused isoquinolines have attracted much attention owing to their biological activities including potent inhibitor of human topoisomerase I and selective inhibition against HIV-1 integrase in vitro (Aubry et al., 2004;Marco et al., 2005;Reddy et al., 1999). We report herein on the single-crystal X-ray diffraction study of the title compound, synthesized from 2-(phenylethynyl)benzaldehyde, sulfonohydrazide and benzyl acrylate in DCE/DMAc.

Experimental
The reaction was performed in test tube under nitrogen atmosphere. 2-(phenylethynyl)benzaldehyde (0.2 mmol) was added to a solution of sulfonohydrazide (0.2 mmol) in DCE (0.5 ml). The mixture was stirred at room temperature for 30 min.
Then AgOTf (7.7 mg, 0.01 mmol) was added and the reaction mixture was heated to 70 o C for 1 h. Subsequently, benzyl acrylate (0.4 mmol) and DMAc (2 ml) were added in the mixture. After completion of reaction as indicated by TLC, the reaction was quenched with aqueous NH 4 Cl (10 ml, 1.0 M), extracted with EtOAc (10 ml), dried by anhydrous Na 2 SO 4 .
Evaporation of the solvent followed by purification on silica gel provided the crystals suitable for X-ray analysis.