- One-pot, three-step preparation of alkyl and aryl alkylcarbamates from S-methyl N-alkylthiocarbamates
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A general procedure for the synthesis of alkyl and aryl alkylcarbamates starting from the corresponding 5-methyl N-alkylthiocarbamates is described. This procedure consists of three steps that are carried out in a one-pot fashion, without isolating the intermediate N-alkylcarbamoyl chlorides or alkyl isocyanates. All the target products were obtained in high yields (16 examples, average yield 91%). To be noted is the recovery of a co-product of industrial interest, dimethyl disulfide, in a half mole amount for each mole of thiocarbamate, with complete exploitation of the reagent. The alkyl isocyanates, if required, can also be isolated in high yields. Georg Thieme Verlag Stuttgart.
- Artuso, Emma,Degani, Iacopo,Fochi, Rita,Magistris, Claudio
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experimental part
p. 1612 - 1618
(2009/04/03)
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- Preparation of carbamoyl halides
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Compounds of formula I, RNHCOCl (I), where R is an optionally substituted alkyl or aryl group, are obtained by chlorinating a compound of formula II, RNHCHO (II), in the absence of a solvent.
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- Studies of Methyl Isocyanate Chemistry in the Bhopal Incident
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Following the methyl isocyanate leak from Tank 610 at the Bhopal plant, the residual material from the tank was analyzed for its contents.Approximately 70percent of the residue was comprised of three cyclic materials: 1,3,5-trimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or methyl isocyanate trimer (5), 1,3-dimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or dimethyl isocyanurate (6), and dihydro-1,3,5-trimethyl-1,3,5-triazine-2,4-(1H,3H)-dione or dihydrotrimethyltriazinedione (7).Minor quantities of methyl-substituted ureas, biurets, and amine hydrochlorides were also found.The composition of the residue was replicated very closely by the products obtained when a mixture of methyl isocyanate (84.4percent), chloroform (12.0percent), and water (3.6percent) was heated at 225 deg C under pressure in a stainless steel reactor.Experimental results are consistent with the view that under these conditions methyl isocyanate reacts initially with water to form 1,3-dimethylurea (1) and 1,3,5-trimethylbiuret (2).At temperatures between 100 deg C and 225 deg C these products decompose to reactive intermediates which further react exothermically to form the aforementioned cyclic materials, trimethylurea, and mono-, di-, and trimethylamine hydrochlorides.The decomposition of 1 and 2 is facilitated by the presence of chloroform and metals.Other experiments involving 13C-enriched chloroform have given support to the proposed mechanisms for formation of 6 and 7.
- D'Silva, Themistocles D. J.,Lopes, Anibal,Jones, Russell L.,Singhawangcha, Sureerat,Chan, John K.
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p. 3781 - 3788
(2007/10/02)
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- Preparation of alkyl isocyanates
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A novel process for the preparation of alkyl isocyanates comprising reacting COX2 and an alkyl amine hydrohalide of the formula wherein R is alkyl of 1 to 3 carbon atoms and X is a halogen either under pressure in an inert organic solvent or under atmospheric pressure in a high boiling organic solvent to form the corresponding alkyl carbamoyl halide, reacting the latter in an organic solvent with an urea of the formula STR1 wherein X' is selected from the group consisting of oxygen and sulfur, R1 and R3 are individually selected from the group consisting of alkyl of 1 to 7 carbon atoms, cycloalkyl of 4 to 6 carbon atoms and phenyl and R2 and R4 are individually selected from the group consisting of hydrogen, alkyl of 1 to 7 carbon atoms, cycyloalkyl of 4 to 6 carbon atoms and phenyl to obtain the corresponding alkyl isocyanate.
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