Georg Meichsner

Synthesis and structure of 2,4-dibromo-3,7-dicyanosemibullvalene. A substitution pattern retarding the cope rearrangement

Abstract The crystal and molecular structure of 2,4-dibromo-3,7-dicyanosemibulvalene( 3b ) synthesized from the bicyclo [3.3.0]octanedione 4 was determined by X-ray analysis; 3b exhibits a higher activation barrier towards degenerate Cope rearrangement than the parent semibullvalene.

15N NMR spectra, tautomerism and diastereomerism of 4,5-dihydro-1H-1,2,3-triazoles

Despite the great number of 4,5-dihydro-1H-1,2,3-triazoles synthesized, 15N NMR data of these heterocycles are extremely rare. The aim of this paper is to present such data and examples of their application. The compounds investigated have been synthesized according to the given references or procedures. Their 15N NMR spectra were measured at natural abundance. For some compounds, the chemical shift assignments were confirmed with the help of 15N labelled material. The influences on 15N chemical shifts of substitution pattern, solvent and concentration were investigated. Additionally, some lanthanide induced shift (LIS) investigations were performed. 13C labelled compounds were employed as tools to provide the assignment of tautomeric structures.