Geometrical isomerism in the S-alkyl thiohydroximate series: a new oxime fragmentation
作者:J. H. Davies、R. H. Davis、P. Kirby
DOI:10.1039/j39680000431
日期:——
S-alkyl thiohydroximates from the results of Beckmann rearrangements on both geometricalisomers. The anti-(alkylthio)-isomers undergo fragmentation under Beckmann conditions. The syn-(alkylthio)-isomers may be converted to the anti-isomers by irradiation with u.v. light. Other evidence concerning the geometry of this series of compounds is discussed.
A general procedure for the synthesis of alkyl and aryl alkylcarbamates starting from the corresponding S-methyl N-alkyl-thiocarbamates 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%)
General procedures are reported to prepare N-alkylureas, N,N'-dialkylureas (both symmetrical and unsymmetrical), and N,N,N'-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60 °C with a molar ratio of DMDTC:amine = 1:2
A General, Facile, and Safe Procedure for the Preparation of <i>S</i>-Methyl <i>N</i>-Alkylthiocarbamates by Methylthiocarbonylation of Primary Aliphatic Amines with <i>S</i>,<i>S</i>-Dimethyl Dithiocarbonate
A general procedure is reported for the selective preparation of S-methyl N-alkylthiocarbamates by methylthiocarbonylation of primary aliphatic amines, employing S,S-dimethyl dithiocarbonate as a phosgene substitute. The reactions are carried out in water at room temperature (20-25 °C), with S,S-dimethyl dithiocarbonate/amine ratios varying between 1:1.2 and 1:2, and with quantitative recovery of the excess amine. The target products are obtained in exceptionally high yields (generally >95%) and with very high purity (generally >99.5%). Also to be noted is the complete chemoselectivity of the reactions, which can be carried out in the presence of hydroxy or aminophenyl groups.
O,S-Dimethyl Carbonodithioate as a Phosgene Substitute for the Preparation of S-Methyl Alkylcarbamothioates and Dialkylcarbamothioates
作者:Rita Fochi、Iacopo Degani、Claudio Magistris
DOI:10.1055/s-0029-1218117
日期:2009.11
conditions for the synthesis of S-methyl dialkylcarbamothioates involved a one-step procedure in a solvent-free system in the presence of triethyl(methyl)ammonium methyl carbonate as a catalyst; yields of the pure products were 85-98%. A mechanism is proposed for the carbamothioate-formation reaction. O,S-dimethyl carbonodithioate - carbamothioates - carbonylation - isomerization - S,S-dimethyl carbonodithioate