H. Mcnab

Diazepines—XXII : 13C NMR spectra of 2,3-dihydro-1,4-diazepinium salts☆

Abstract The 13 C NMR spectra of a number of 2,3-dihdyro-1,4-diazepinium salts, like 1 H NMR spectra, confirm shape, and charge distribution for these compounds. The ring has a half-chair shape which is inverting rapidly at room temperature. The atoms in the conjugated portion of the ring show alternating polarity, and phenyl groups attached to these positions act, respectively, as electron-donors or electron-acceptors. A methyl substituent in the saturated portion of the ring shows equal preference for quasi-equatorial and quasi-axial conformations. Some comparisons are drawn between present results and similar results obtained with related benzene derivatives.

Gas-phase pyrolysis of 2,3-dihydro-1,4-diazepines: involvement of the saturated portion of the ring in chemical reactions and novel cis–trans isomerisation of a fused ring system

Flash vacuum pyrolysis of 2,3-dihydro-1,4-diazepines in the range 450–550 °C involves interaction of the saturated portion of the molecule with the vinamidine system and causes 1,5-hydrogen shifts which have been established by deuterium labelling experiments; at higher temperatures, ring contraction occurs to give pyrazines as major products.

Diazepines, Part 28. Crystal and molecular structures of some dihydrodiazepinium salts and correlation with their reactivity and spectra

The crystal and molecular structures of 6-bromo-5-methyl-7-phenyl-, 6-bromo-5,7-diphenyl- and 6-bromo-1,4-dimethyl-dihydrodiazepinium perchlorates have been determined. Some features of these structures, and of other recently determined structures of dihydrodiazepinium salts are discussed and compared with other properties, particularly the reactivity of 6-halogenodihydrodiazepinium salts towards nucleophiles, and the spectra and structure of 5,7-diphenyl derivatives.

7-Phenyl-2,3,4,5-tetrahydro-1H-1,4-diazepin-5-one

The refinements were carried out based on all the reflections with IFol 4 o. The threshold, I > 2cr(/), was used only for calculation of the R factor. The positions of all the H atoms were calculated geometricallYoand a riding model was used in their refinement (C--H 0.96 A). Ui~,,(H) values were refined. For all compounds, data collection: AFC/MSC Diffrac- tometer Control System (Rigaku Corporation, 1993); cell re- finement: AFC/MSC Diffractometer Control System; data re- duction: local programs; program(s) used to solve structure: CRYSTAN-GM (Edwards et al., 1996); program(s) used to re- fine structure: CRYSTAN-GM; molecular graphics: CRYSTAN- GM; software used to prepare material for publication: CRYSTAN-GM. Abstract The geometry of the title diazepinone, CIIHI2N20, reflects the presence of cross-conjugated amide and vinylogous amide functions. The packing is dominated by hydrogen-bonding interactions which link the mol- ecules into corrugated sheets.