Carbamates I: structural and conformational study of eight methoxyphenyl-N-pyridinylcarbamates

Abstract

A 3×3 isomer grid of nine methoxyphenyl-Npyridinylcarbamates (C 13 H 12 N 2 O 3 ) as CxxOMe (x = para-/meta-/ortho-) was synthesized and studied to determine the crystal structures and correlate structural relationships from both ab initio calculations and the solid-state using conformational analysis. Eight of nine isomers crystal structures were determined using single crystal X-ray diffraction. All isomers form N-H…N hydrogen bonds as primary interaction, with one isomer (CmmOMe) forming a relatively unusual disordered hydrogen bonded trimer via the N-H…N interactions, while the CoxOMe isomers form the N-H…N hydrogen bonded dimers. In all isomers additional C-H…O interactions aid aggregation, whereas in most of isomers the methoxy group is engaged in important C-H…O hydrogen bonding patterns.The solid state and the modelled conformations are mismatched in 3 of 8 molecules in which methoxy groups and meta-methoxyphenyl rings (mOMe) of the solid state structures adopt meta-stable or unstable conformations as compared to the optimised computational models.

Three derivatives of 4-fluoro-5-sulfonylisoquinoline

“…In the 1 H NMR spectrum of (II), the multiplicity of the amide proton is triplet ( 5.34), but doublet ( 5.40) for the nonfluorinated analogue, suggesting spin-spin coupling between the amide N-H group and the active 19 F nuclei (J N-HÁ Á ÁF = 7.1 Hz). Similar through-space nuclear spin-spin couplings due to intramolecular N-HÁ Á ÁF hydrogen bonds have been observed for 2-fluoro-N-(pyridinyl)benzamides, the NÁ Á ÁF distances being 2.722 (5)-2.753 (6) Å (Mocilac et al, 2012). The 2-fluorophenylsulfonamides do not show such intramolecular spin-spin coupling (Samarakoon et al, 2010), and this agrees with the fact that the conformations of these molecules are not suitable for the formation of intramolecular N-HÁ Á ÁX hydrogen bonds (X = Cl: Fernandes et al, 2011; Shakuntala et al, 2011; X = I: Arshad et al, 2011).…”

High-Z′ structures of organic molecules: their diversity and organizing principles

“…Wholemolecule disorder (e.g. HAXLAV; Mocilac et al, 2012) may indicate a missed modulation unless the disorder has little effect on the van der Waals surface of the molecule. The case of MACCID02 (Z 0 = 4, Z * = 6, substantial disorder; Bowes et al, 2003) and the corrected structure MACCID03 (Z 0 = Z * = 4, no disorder; Cascarano et al, 2013) is cautionary.…”

Entry point into new trimeric and tetrameric imide-based macrocyclic esters derived from isophthaloyl dichloride and methyl 6-aminonicotinate

“…Differences reflect additional molecular strain in the trezimide (EsIO) 3 compared with the tennimide (EsIO) 4 as well as crystal-packing requirements. The ease with which the isophthaloyl groups can twist/distort in comparison with the imide hinge has been rationalized in terms of energy barriers which are considerably lower for the isophthaloyl groups (Mocilac, 2012). Hence, molecular strain is relieved with conformational change arising mainly in the isophthaloyl groups.…”