Patent GB-843331-A (GB)
Title: A process for the manufacture of carbamates and novel carbamates
IPC: C07C271/06
Filed: 1958-08-11
Abstract: The invention comprises, (1) the monocarbamates of 2 : 2-di-substituted-butanediol-(1 : 3)s of the general formula: <FORM:0843331/IV(b)/1> (wherein R1 and R2 are methyl, ethyl, propyl or allyl groups together containing from 3 to 6 carbon atoms) prepared by reacting the free diol either with a carbamoyl halide (preferably the chloride) or with phosgene or a chloroformic acid ester (in the presence of an acid-binding agent) and treating the product with excess ammonia; (2) the specific compounds 2 : 2-diethyl-, 2-methyl-2-n-propyl-, 2 : 2-dipropyl- and 2 :2-diallyl-butanediol-(1 : 3) monocarbamates having melting points of 100 DEG C., 99-100 DEG C., 90 DEG C., and 99 DEG C. respectively, and the first named compound having the following bands (cm-1) in the infra-red spectrum (potassium bromide pellet):-3356, 3195, 2967, 1701, 1642, 1464, 1443, 1412, 1383, 1376, 1353, 1326, 1307, 1193, 1131, 1107, 1058, 1020, 1000, 970, 906, 882, 791, 772 and 686; and (3) the processes outlined above.  It is stated that the carbamate group in these compounds is believed to be attached to the primary carbon atom.  When equimolar proportions of phosgene and acid-binding agent, e.g. pyridine, quinoline, N : N-dimethylaniline or triethylamine, are used, preferably in the cold e.g.-10 DEG C. the product is the mono-chlorocarbonyl compound, whereas when 2 mols of acid-binding agent per mol of phosgene are used the product is a 5 : 5-disubstituted-4-methyl-metadioxanone-(2).  Either of these products on treatment with ammonia yields the desired mono-carbamate.  When a chloroformic acid ester is used the reaction may be conducted at ordinary temperatures using equimolar proportions of the ester e.g. the ethyl, or, preferably, the phenyl ester, and the acid-binding agent, and the 2 : 2-disubstituted butanediol-(1 : 3)-phenyl formate formed, for example, then treated with ammonia.  The molar amount of carbamoyl halide, phosgene or chloroformic ester used may be greatly in excess of the molar amount of diol.  Examples illustrating these processes are given and the reduction of 2 : 2-diallyl butanediol monocarbamate to the 2 : 2-dipropyl compound is also referred to.  2 : 2-Disubstituted-butanediol-(1 : 3)s of the above general formula are prepared by reducing a :a -disubstituted-acetoacetic esters with lithium aluminium hydride.  Ethyl a -methyla -propyl-acetoacetate is prepared by condensing ethyl acetoacetate and allyl bromide to form ethyl a -allyl-acetoacetate, condensing this with methyl bromide to form ethyl a -allyla -methyl-acetoacetate and reducing this with hydrogen and palladium catalyst.  Ethyl dipropyl-acetoacetate is prepared by condensing ethyl acetoacetate with 2 mols of allyl bromide to form ethyl diallyl-acetoacetate and reducing this with hydrogen and palladium charcoal catalyst.ALSO:Oral pharmaceutical preparations e.g. in the form of tablets contain as essential active ingredient a monocarbamate of a 2 : 2-disubstituted-butanediol-(1 : 3) of the general formula:  <FORM:0843331/VI/1> wherein R1 and R2 are methyl, ethyl, propyl or allyl groups together containing from 3 to 6 carbon atoms).  The 2 : 2-diethyl-, 2-methyl-2-propyl-, 2 : 2-dipropyl- and 2 : 2- diallyl-compounds are specifically referred to (see Group IV(b)).