ChemInform Abstract: Reaction of Chloroacetylenephosphonates with Neutral Nucleophiles.

Abstract

ChemInform Abstract Reaction of the phosphonates (I) with the nucleophilic reagents (II), containing a primary amino group and a second nucleophilic centre, yields the phosphorylated benzimidazoles or benzoxazoles (III). The dihydrooxazoles (V) are obtained from (I) and ethanolamine (IV) in an analogous manner. (Mechanism).

Ab Initio Study of Molecular Properties and Decomposition Products of 1-AzidoalkynesA Challenge for Experimentalists

“…Since the 1950s, many groups have tried to generate 1-azidoalk-1-ynes, but these species are a mystery even today. − Several attempts at preparing the title compounds were unsuccessful or led to unwanted products. − For example, the reaction of (phenylethynyl)sodium or alkyl-1-ynyllithiums and tosyl azide yielded only 1,2,3-triazole derivatives instead of the target compounds. , Even in the case of generating 1-azido-2-phenylethyne ( 2 ) in situ, the sequential chemistry of such a short-lived intermediate is still unclear (Scheme ). Thus, treatment of the precursor 1 with sodium azide in dimethyl sulfoxide (DMSO) was said to lead in low yield to product 4 , which was explained by formation of intermediate 2 followed by the loss of nitrogen and trapping of the nitrene 3 by DMSO. − Alternatively, starting material 5 is transformed under a variety of conditions and in high yield into cis - and trans -dicyanostilbenes 8 , which are formally dimers of the carbene 6 . , However, the known trapping products of 6 including the cyclopropane framework could not be detected when 5 was treated in the presence of cyclohexene or diphenylacetylene.…”

Dialkyl 1-Alkynylphosphonates: a Range of Promising Reagents

“…[87] The phosphorus-containing ynamines have been prepared through the reaction of diethyl 2-chloroethynylphosphonates 6 with dialkylamines. [115] Some of these compounds were also prepared by heating 6 with trimethylamine (100% excess) in a sealed tube at 150Ϫ160°C. [116] Formation of ynaminophosphonates by electrochemical synthesis has also been reported.…”

“…[119] The reaction of ketenimines with water in the presence of catalytic amounts of HCl proceeds smoothly and leads to a high yield of the corresponding amide. [120] Reactions of 2-chloroethynylphosphonates 6 have also been studied with a number of charged (EtO Ϫ , tBuO Ϫ , PhO Ϫ ) [121] and neutral [122] nucleophiles containing one or two nucleophilic centers. Treatment of diethyl 2-chloroethynylphosphonate 6 with binucleophilic reagents such as ortho-phenylenediamine, ortho-aminophenol, and 2-aminoethanol leads to phosphorylated benzimidazoles, benzoxazoles and 4,5-dihydroxazoles, by a mechanism involving initial substitution of the halogen followed by addition of the second nucleophilic center at the same carbon atom.…”

“…Treatment of diethyl 2-chloroethynylphosphonate 6 with binucleophilic reagents such as ortho-phenylenediamine, ortho-aminophenol, and 2-aminoethanol leads to phosphorylated benzimidazoles, benzoxazoles and 4,5-dihydroxazoles, by a mechanism involving initial substitution of the halogen followed by addition of the second nucleophilic center at the same carbon atom. [122] …”

“…[117] The ynaminophosphonates readily undergo all of the reactions characteristic of ynamines: hydration by water with the formation of acetamides, addition of alcohol with the formation of the corresponding vinyl ethers. [115] The use of tert-butylamine in the reaction with 6 also induces the replacement of halogen, but the reaction is accompanied by isomerisation, giving almost quantitative yields of stable ketenimines. [118,119] The presence of two hydrogen atoms at the nitrogen in the amines permits subsequent prototropic isomerisation with the formation of ketenimines.…”