Condensation of triethylorthoformate with cyclic methylene-active compounds gives rise to ethoxymethylene-, bismethenyl- or triscompounds of type A, B or C resp. An explanation of this different behavior can be obtained by comparing the π-electron densities at the β-carbon atom of the exocyclic double blond of ethoxymethylen- and bismethenyl-compounds, which are calculated using HMO-theory. These calculationes show a limiting electron density, which can be used to explain the lack of further reaction to bis- and triscompounds, when certain heterocyclic active methylenes are used.
Reactions of some heterocyclic diketones have been studied and, their behavior found in agreement with theoretical concepts
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Zeitschrift für Naturforschung B is an international scientific journal which publishes original papers, microreviews, and letters from all areas of inorganic chemistry, solid state chemistry, coordination chemistry, molecular chemistry, and organic chemistry.