A rapid halogen exchange between HCBr,, HCBr21, HCBrI,, and HCI, occurred in the presence of conc. sodium hydroxide and a quaternary ammonium salt. Trapping experiments with various alkenes gave cyclopropane derivatives only in 3 cases. Depending on the nucleophilicity of the alkene and the haloform, different proportions of CBr,, CBrI, and CI, adducts were obtained. The most nucleophilic acceptor trapped those carbenes preferentially that were formed by elimination of iodide.
The known hypochlorite oxidation of thioureas to the corresponding carbodiimides becomes faster and more convenient by the use of PTe. Aromatic thioamides are transformed into 3,5-substituted 1,2,4-thiadiazoles by the same technique, and substituted 2,5-diamino-l,3,4-thiadiazoles as well as 2-phenylaminobenzimidazoles and -benzoxazoles can be prepared similarly.
Abstract. Trimerizations of isocyanates give isocyanurates (N.N.N-trisubstituted 1,3,5-triazinetriones) in an exothermic, high yield PTC process. Catalysis by various inorganic salts combined with onium salts or crown ethers is effective, Aliquat 336 being the best catalyst.
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