Synthesis of Substituted Pyrazoles from Aryl-sydnones.

BACKGROUND: In this current work, a new synthesis strategy was developed to obtain 1,3,4-trisubstituted pyrazoles derivatives. METHODS: A series of 1,3,4-trisubstituted pyrazoles have been prepared via 1,3-dipolar cycloaddition reaction of 3-phenylsydnones with a variety of alkenes derivatives, symmetric and non-symmetric alkynes derivatives, N-phenyl-maleimide, N-benzylmaleimides, and maleic anhydride under conventional manner. RESULTS: Moreover, in this work, it has been demonstrated that the 4-bromopyrazole intermediates can be further functionalized by a combination of Suzuki-Miyaura crosscoupling reactions with aryl-boronic acids and N-arylation reactions of anilines. CONCLUSION: In summary, we have developed a new method to obtain 1,3,4 triarylated pyrazoles through 3-phenylsydnone 1,3-dipolar cycloadditions. By comparing the different reactions, it is apparent that high temperatures and xylene as solvent are key to achieving pyrazoles derivatives. The best yields were observed for symmetric and non-symmetric alkynes as dipolarophiles.

Crystal structure of 2-meth-oxy-1-nitro-naphthalene.

The asymmetric unit of the title compound, C11H9NO3, contains two mol-ecules, A and B. In mol-ecule A, the dihedral angle between the planes of the naphthalene ring system (r.m.s. deviation = 0.003 Å) and the nitro group is 89.9 (2)°, and the C atom of the meth-oxy group deviates from the naphthyl plane by 0.022 (2) Å. Equivalent data for mol-ecule B are 0.008 Å, 65.9 (2)° and -0.198 (2) Å, respectively. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions, forming [100] chains of alternating A and B mol-ecules. Weak aromatic π-π stacking contacts, with a range of centroid-centroid distances from 3.5863 (9) to 3.8048 (9) Å, are also observed.

Crystal stucture of methyl 2-({[2-(meth-oxy-carbon-yl)phen-yl]carbamo-yl}amino)-benzoate.

In the title compound, C17H16N2O5, the dihedral angles between the central urea [N-C(=O)-N] fragment and its attached benzene rings are 20.20 (14) and 24.24 (13)°; the dihedral angle between the aromatic rings is 42.1 (1)°. The mol-ecular conformation is consolidated by two intra-molecular N-H⋯O hydrogen bonds, which both generate S(6) rings. In the crystal, inversion dimers linked by pairs of C-H⋯O inter-actions generate R 2 (2)(14) loops. The dimers are linked by further C-H⋯O inter-actions into (011) sheets.