Abstract
Synthesis of stable phosphorus ylides from 3, 5-dimethylpyrazole and kinetic investigation of the reactions by UV spectrophotometry
Highlights
Development of simple synthetic routes for widely used organic compounds from readily available reagents is one of the major tasks in organic chemistry.1 Phosphorus ylides are reactive systems, which take part in many valuable reactions in organic synthesis2-12 and are most often prepared by treatment of a phosphonium salt with a base
Most of the phosphonium salts are prepared from the reaction of a phosphine and an alkyl halide3-7 though they can be obtained by Michael addition of phosphorus nucleophiles to activated olefins
The reaction of triphenylphosphine 1 with dialkylacetylene dicarboxylates 2 (2a or 2b) in the presence of a NH-acid 3 led to the corresponding stable heterocyclic phosphorus ylides 4 (4a or 4b) in excellent yields
Summary
Development of simple synthetic routes for widely used organic compounds from readily available reagents is one of the major tasks in organic chemistry.1 Phosphorus ylides are reactive systems, which take part in many valuable reactions in organic synthesis2-12 and are most often prepared by treatment of a phosphonium salt with a base. The reactions of 3,5-dimethylpyrazole 3 with dialkyl acetylenedicarboxylates 2 in the presence of triphenylphosphine 1 were carried out in diethyl ether solvent at room temperature and were complete within a few hours. This, provided the opportunity to fully investigate the kinetics of the reaction between triphenylphosphine 1, di-tert-butyl acetylenedicarboxylate 2b and 3,5-dimethylpyrazole 3 at 330 nm in the presence of 1,4-dioxane as solvent.
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