Synthesis, Crystal Structures, and DFT Calculations of Three New Cyano(phenylsulfonyl)indoles and a Key Synthetic Precursor Compound

Abstract

Three cyano-1-(phenylsulfonyl)indole derivatives, 3-cyano-1-(phenylsulfonyl) indole, (I), 2-cyano-1-(phenylsulfonyl)indole, (II), and 2,3-dicyano-1-(phenylsulfonyl) indole, (III), and a key synthetic precursor 1-(phenylsulfonyl)-1-(1,1-dimethylethyl) indole-3-carboxamide, (IV), have been synthesized and their structures determined by single crystal X-ray crystallography. (I), C15H10N2O2S, is orthorhombic with space group P 212121 and cell constants: a = 4.9459(3) A, b = 10.5401(7) A, c = 25.0813(14) A, V = 1307.50(14) A3 and Z = 4. (II), C15H10N2O2S, is monoclinic with space group C 2/c and cell constants: a = 18.062(2) A, b = 11.293(2) A, c = 15.922(3) A, α = 90°, β = 124.49(2)°, g = 90°, V = 2676.7 A3 and Z = 8. (III), C16H9N3O2S, is triclinic with space group P-1 and cell constants: a = 8.1986(8) A, b = 9.6381(11) A, c = 9.8113(5) A, α = 95.053(6)°, β = 101.441(6)°, g = 108.071(9)°, V = 713.02(11) A3 and Z = 2. (IV), C19H20N2O3S, is orthorhombic with space group P ccn and cell constants: a = 13.7605(8) A, b = 27.3177(14) A, c = 9.7584(6) A, α = 90°, β = 90°, g =90°, V = 3668.2(4) A3 and Z = 8. All four compounds have the same indole nitrogen phenylsulfonyl substituent and (I), (II), and (III) are nitrile derivatives. (IV) is a tert-butylamide. In the crystals, the dihedral angle between the mean planes of the indole and phenylsulfonyl groups are 85.4(2)° (I), 87.2(7)° (II), 75.1(7)° (III), and 88.6(2)° (IV), respectively. Additionally, DFT geometry-optimized molecular orbital calculations were performed and frontier molecular orbitals of each compound are displayed. Correlation between the calculated molecular orbital energies (eV) for the surfaces of the frontier molecular orbitals to the electronic excitation transitions from the absorption spectra of each compound has been proposed.