GB409732A - Process for the catalytic synthesis of heterocyclic bases - Google Patents

Abstract

Dehydrating and hydrogenating catalysts are manufactured by the following methods, which are described in respect of nickel catalysts but are stated to be applicable also to the production of copper and cobalt catalysts: (a) reduction of any nickel salt, supported or unsupported, by hydrogen or other reducing agents; (b) treatment of a nickel alloy such as nickel-aluminium or nickel-silicon with aqueous alkalies; (c) reduction of nickel salts in admixture with salts of other metals of group VIII or I of the periodic table acting as co-catalysts; (d) reduction of nickel salts mixed with promoters such as oxides of metals of groups II, III, IV, V and VI of the periodic table; (e) mechanical subdivision of massive nickel; (f) anodic oxidation of nickel surfaces followed by reduction; (g) colloidal dispersion of metallic nickel; (h) precipitation by more electropositive metals such as aluminium and zinc. The products are employed in the manufacture of tertiary heterocyclic bases by reacting an organic hydroxy compound with a nitrogen-heterocyclic base containing replaceable hydrogen attached to a nuclear nitrogen atom, or with an unsaturated nitrogen-heterocyclic base together with hydrogen, in the liquid phase under superatmospheric pressure at about 175--250 DEG C. Specification 394,576 is referred to.ALSO:Tertiary heterocyclic bases are manufactured by reacting an organic hydroxy compound with a nitrogen-heterocyclic base containing replaceable hydrogen attached to a nuclear nitrogen atom, or with an unsaturated nitrogen-heterocyclic base together with hydrogen, the reaction being effected in the liquid phase, under superatmospheric pressure, e.g. at about 100 atmospheres, at a temperature of about 175--250 DEG C., and in the presence of a dehydrating and hydrogenating catalyst, particularly one containing nickel, copper or cobalt. The molecular ratio of the amounts of base to hydroxy compound is preferably about 1 : 2. Suitable catalysts containing nickel may be prepared by (a) reduction of any nickel salt, supported or unsupported, by hydrogen or other reducing agents; (b) treatment of a nickel alloy such as nickel-aluminium or nickel-silicon with aqueous alkalies; (c) reduction of nickel salts in admixture with salts of other metals of group VIII or I of the periodic table acting as co-catalysts; (d) reduction of nickel salts mixed with promoters such as oxides of the metals of groups II, III, IV, V and VI of the periodic table; (e) mechanical subdivision of massive nickel; (f) anodic oxidation of nickel surfaces followed by reduction; (g) colloidal dispersion of metallic nickel; (h) precipitation by more electropositive metals such as aluminium and zinc. A reduced nickel catalyst prepared according to Specification 394,576, [Group III], may be used. Copper and cobalt catalysts prepared in similar ways may also be employed. Suitable nitrogen heterocyclic bases are: piperidine, a - and b -pipecoline, a -ethylpiperidine, and other alkyl piperidines, a - benzylpiperidine, 1 - a - or g - piperidyl-2 - phenylethane, pyrrolidine, a - methyl - pyrrolidine, a -piperidylpyrrolidine (obtainable by hydrogenating pyridylpyrrole over nickel at 175--200 DEG C.), pyrazoline, pyrazolidine, indoline, tetrahydrocarbazole, hexahydrocarbazole, dihydroglyoxalines, a -phenylpiperidine, dipiperidyls, lupetidines, copellidines, tetrahydroquinoline, decahydroquinoline, tetrahydroquinaldine, decahydroquinaldine, and dihydroacridine. The parent unsaturated ring compounds may also be used in conjunction with hydrogen. The hydroxy compounds may be aliphatic, alicyclic, aryl, aralkyl or heterocyclic, including hydroxy heterocyclic compounds having alkyl substituents. Specified compounds are: methanol, ethanol, propanol, butanol, a - and b -naphthol, decahydronaphthols, tetrahydronaphthols, methylcyclohexanol, ethylcyclohexanol, cyclohexanol, phenylethyl alcohol, furfuryl alcohol, cresols, tetrahydrofurfuryl alcohol, 4-hydroxypyridine and 4-hydroxypiperidine. In examples: (1) piperidine is reacted with ethanol under a pressure of 100 atmospheres of nitrogen at 200 DEG C. in the presence of a reduced nickel catalyst prepared by the process of Specification 394,576, producing N-ethylpiperidine; (2) a -methylpiperidine is reacted with ethanol in a shaking autoclave under a pressure of 100 atmospheres of hydrogen at 200 DEG C. in the presence of the catalyst of (1), yielding N-ethyl-a -methylpiperidine; (3) a -methylpiperidine is reacted with butanol-1 under the conditions enployed in (1) to produce N-n-butyl-a -methylpiperidine; (4) piperidine and ethanol are reacted under the conditions employed in (2), producing N-ethylpiperidine; (5) piperidine is reacted with butanol under the conditions employed in (2), yielding N-n-butylpiperidine; (6) piperidine is reacted with cyclohexanol under the conditions employed in (2), to produce N-cyclohexylpiperidine; (7) pyridine is hydrogenated in a high pressure autoclave in the presence of ethanol at 200 DEG C. and under a pressure of 70--170 atmospheres, yielding N-ethylpiperidine. The Specification as open to inspection under Sect. 91 comprises also the carrying out of the reaction under atmospheric pressure. It contains an additional example according to which piperidine and ethyl alcohol are reacted in the presence of the catalyst employed in the other examples, at 200 DEG C. in a vessel from which air has been removed by means of nitrogen under atmospheric pressure. Benzyl alcohol is specified as an additional starting material. This subject-matter does not appear in the Specification as accepted.