Ambiguousness of GC-MS identification of spiro[2.4]hepta-4,6-diene in natural objects

Recent advances in the catalytic cyclopropanation of unsaturated compounds with diazomethane

The main achievements and development trends of the past 10–15 years related to the catalytic cyclopropanation of unsaturated compounds with diazomethane are integrated and analyzed. The attention is focused on the most efficient catalysts based on palladium compounds. Data on the effects of substrate structure and nature of catalyst components on the regio- and stereoselectivity of these reactions are systematized. Characteristic features of safe methods for diazomethane generation are considered, including the use of membrane technologies and continuous-flow and in situ preparation methods, which have prospects for industrial application.

The bibliography includes 281 references.

Comparative gas chromatographic/mass spectrometric characterization of di- and trialkyl phosphites

RATIONALE

Homologous series of alkyl esters of phosphorus-containing acids, namely, dialkyl phosphonates (synonym: dialkyl phosphites) and trialkyl phosphites, were characterized by electron ionization (EI) mass spectra and gas chromatographic retention indices (GC RI) on semi-standard non-polar stationary phases. It is confirmed that GC/MS characterization of any sets of homologues should not be restricted to independent registration of these analytical parameters. Their joint processing in the form of so-called homologous increments of GC RIs means, firstly, a novel way of evaluating the chromatographic polarity of analytes and, secondly, a new algorithm for the prediction of their molecular weights if no peaks of molecular ions are registered in the mass spectra.

METHODS

A standard GC/MS technique, including determination of GC RIs on semi-standard nonpolar stationary phases in temperature-programmed regime and electron ionization (EI) mass spectra was used.

RESULTS

A total of 31 dialkyl phosphonate homologues and 37 trialkyl phosphite homologues were characterized by EI mass spectra and GC RIs for the first time. Joint processing of these analytical parameters allows the calculation of so-called homologous increments of GC RIs, which are useful parameters for evaluating the chromatographic polarity of analytes and predicting their molecular weights.

CONCLUSIONS

GC/MS characterization of any sets of homologues should not be restricted to independent registration of the mass spectra and chromatographic retention parameters. Their joint processing in the form of so-called homologous increments of GC retention indices means, firstly, a novel way of evaluating the chromatographic polarity of analytes and, secondly, a new algorithm for predicting their molecular weights.