Experimental and calculated structural parameters of 4-(2-methoxycarbonyl-ethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylic acid benzyl ester

Crystal structure of 4-(2-methoxycarbonyl-ethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylic acid benzyl ester has been solved by X-ray diffraction. The crystals are triclinic, space group P1¯, with a=5.4435(18) Å, b=12.248(2) Å, c=13.6769(15) Å, α=70.274(12)°, β=81.630(15)°, γ=77.60(2)°, Z=2 and R=0.0519. The molecules are strongly linked in dimers by hydrogen bonds, forming rings with R22(10) as the graph descriptor. The pyrrolic ring, slightly distorted from the C2v symmetry, is almost planar. This plane makes an angle of 75.5(1)° with the L.S. plane containing the methoxy-carbonyl group and an angle of 13.6(1)° with the L.S. plane containing the benzyl group. The internal cohesion of the crystal is supported by three C-H…π intermolecular interactions, with H…Cg (ring centroid) distances ranging from 3.060 to 3.377 Å. Several calculations were performed for the dimer such as density functional theory with a hybrid functional B3LYP, semi-empirical self-consistent field (AM1 and PM3) and self-consistent field molecular orbital Hartree-Fock (SCF-MO HF) method. The latter calculation was repeated for the isolated molecule. In all cases the minimum of the energy is achieved with the substituents assuming a more perpendicular position to the central aromatic ring than is experimentally observed.