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The reaction of a substituted amide with phosphorus oxychloride gives a substituted chloroiminium ion (2), also called the Vilsmeier reagent. The initial product is an iminium ion (4b), which is hydrolyzed to the corresponding ketone or aldehyde during workup. [7] The Vilsmeier–Haack reaction
Vilsmeier reagent is the active intermediate in the formylation reactions, the Vilsmeier reaction or Vilsmeier-Haack reaction that use mixtures of dimethylformamide and phosphorus oxychloride to generate the Vilsmeier reagent, which in turn attacks a nucleophilic substrate and eventually hydrolyzes to give formyl.
One example involves conversion of formamides to isonitriles (isocyanides); [14] primary amides to nitriles: [15] RC(O)NH 2 + POCl 3 → RCN + P(O)OHCl + 2 HCl. In a related reaction, certain aryl-substituted amides can be cyclized using the Bischler-Napieralski reaction. Such reactions are believed to proceed via an imidoyl chloride. In ...
The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement of an oxime functional group to substituted amides. [1] [2] The rearrangement has also been successfully performed on haloimines and nitrones.
In the Morgan–Walls reaction, the linker between the aromatic ring and the amide nitrogen is an ortho-substituted aromatic ring. This N-acyl 2-aminobiphenyl cyclizes to form a phenanthridine. The Pictet–Spengler reaction proceeds from a β-arylamine via condensation with an aldehyde. These two components form an imine, which then cyclizes ...
This reaction is used to produce around 10,000 tonnes of PCl 5 per year (as of 2000). [6] PCl 3 + Cl 2 ⇌ PCl 5 (ΔH = −124 kJ/mol) PCl 5 exists in equilibrium with PCl 3 and chlorine, and at 180 °C the degree of dissociation is about 40%. [6] Because of this equilibrium, samples of PCl 5 often contain chlorine, which imparts a greenish ...
Weinreb and Nahm originally proposed the following reaction mechanism to explain the selectivity shown in reactions of the Weinreb–Nahm amide. Their suggestion was that the tetrahedral intermediate (A below) formed as a result of nucleophilic addition by the organometallic reagent is stabilized by chelation from the methoxy group as shown. [1]
The von Braun amide degradation is the chemical reaction of a monosubstituted amide with phosphorus pentachloride or thionyl chloride to give a nitrile and an organohalide. [1] It is named after Julius Jacob von Braun, who first reported the reaction. [2] [3] The von Braun amide degradation