Intra‐ and Intermolecular C(sp²)–H···O Hydrogen Bonds in a Series of Isobenzofuranone Derivatives: Manifestation and Energetics

Abstract

Derivatives 2-6 were prepared as models for studying intraand intermolecular C(sp 2 )-H···O hydrogen bonding. Their Xray structures confirm the presence of intramolecular hydrogen bonds in derivatives of the "a" series: the corresponding C···O distances vary between 2.91 and 2.97 Å. The corresponding 13 C-1 H coupling constants are increased by about 7.5 Hz, and the 1 H chemical shifts in CDCl 3 are 9.1-10.7 ppm. No intramolecular hydrogen bonds can form in derivatives of the isomeric "b" series. In this series, the chemical shifts of the corresponding aromatic protons exhibit strong solvent dependency; in particular, they are as sensitive as the proton in chloroform to the presence of DMSO. The vinylic protons activated by the electron-accepting COOR groups behave similarly. Quantum mechanical calculations in the gas phase and in DMSO reproduce the experi-

A Regio‐ and Stereoselective Carbonylative Approach to Alkyl (Z)‐2‐[3‐Oxoisobenzofuran‐1‐(3H)‐ylidene]acetates

“…157.8, 136.1, 135.3, 132.5, 128.2, 126.5, 125.3, 102.5, 60.9, 14.3; GC/MS: m/z =218 (M + , 18), 190 (24), 173 (100), 146 (66), 118 (5), 105 (17), 89 (46), 76 (17); HRMS‐ESI ( m/z ): [(M+H) + ] calcd for (C 12 H 11 O 4 ): 219.0652; found, 219.0648. The spectroscopic data were in good agreement with those reported …”

Molecular Structure, Intramolecular Hydrogen Bonding, Solvent‐Induced Isomerization, and Tautomerism in Azolylmethylidene Derivatives of 2‐Indanone

“…[27] Unlike the present case, due to the absence of labile hydrogen atoms, the isomerization described by Niebel et al [27] proceeded via a zwitterion intermediate resulting from the nucleophilic attack of the DMSO oxygen atom on the positively charged carbonyl carbon with subsequent rotation about the exocyclic C-C bond and DMSO elimination. [27] Unlike the present case, due to the absence of labile hydrogen atoms, the isomerization described by Niebel et al [27] proceeded via a zwitterion intermediate resulting from the nucleophilic attack of the DMSO oxygen atom on the positively charged carbonyl carbon with subsequent rotation about the exocyclic C-C bond and DMSO elimination.…”

“…Recently, a similar DMSO-assisted isomerization was observed for the series of 2-[3-oxoisobenzofuran-1(3H)-ylidene]acetate derivatives (Scheme 7). [27] Unlike the present case, due to the absence of labile hydrogen atoms, the isomerization described by Niebel et al [27] proceeded via a zwitterion intermediate resulting from the nucleophilic attack of the DMSO oxygen atom on the positively charged carbonyl carbon with subsequent rotation about the exocyclic C-C bond and DMSO elimination.…”

Crystallographic and ab initio study of pyridine CH–O interactions: linearity of the interactions and influence of pyridine classical hydrogen bonds

“…Regions are defined by angle φ: N region has angle φ values from 0-30° and 20 330-360° (in case of para substituted pyridines only in range 0-30° as it is symmetric), S region is the region around substituent, while CH region can be in a range 30-330° (in case of para substituted pyridines only in range 30-180° as it is symmetric), depending on the position of substituent. We did not search for 25 CH/O interactions in the N and S regions. Namely, interactions in N region are governed by strong tendency of nitrogen atom for hydrogen bonds, while interactions in S region are strongly influenced by the nature of the substituent.…”