GB799924A - N-vinylation of lactams - Google Patents

Abstract

Lactams containing an > NH group in the ring are N-vinylated by dissolving acetylene in a solution of an alkali metal or alkaline earth derivative of the lactam in the lactam, either alone in liquid form or in admixture with an organic liquid in which the lactam is soluble or with which it is miscible and which is inert with respect to the reactants under the reaction conditions, at a temperature below 50 DEG C. and at a pressure not greater than 20 atmospheres gauge and thereafter heating this solution to a temperature within the range 110-200 DEG C. at a pressure such that no gaseous phase is allowed to form during the reaction. The solution of lactam derivative in the lactam may be made by mixing the lactam with sodium or potassium hydroxide or an alkaline earth metal oxide or hydroxide and distilling off the water formed; the alkali metals themselves and their oxides may also be used. Organic solvents which may be present include tetrahydrofuran, dioxane, acetonitrile, toluene and, less suitably, vinyl pyrrolidone. Sodium pyrollidone tends to precipitate from its solution to some extent, especially in the presence of tetrahydrofuran, and when employed its solution should be prepared at slightly raised temperature or a dispersing agent such as aluminium stearate, should be present for optimum results. Preferably, 2 to 5 per cent of the lactam is converted into its alkali metal or alkaline earth metal derivative. The vinylation is preferably effected continuously. In typical examples: (1) a mixture of pyrrolidone and tetrahydrofuran in which potassium metal has been dissolved (weight proportions 50 : 25 : 1) is passed down a packed column counter-currentwise to acetylene at 15 DEG C. and under 20 atmos. gauge pressure and the resulting acetylene saturated liquid is pumped into a stainless steel tube maintained at 155 DEG C. and 120 atmospheres gauge; the reacted mixture flows out through a water-cooler and pressure controller into a receiver at atmospheric pressure and is distilled to recover the solvent and vinyl-pyrrolidone product; the residue comprising unchanged pyrrolidone and its potassium derivative is mixed with the recovered solvent and fresh pyrrolidone, and the above procedure is repeated; this recycling of the residues may be continued until the proportion of polymeric by-products including ethylidene dipyrrolidone becomes excessive; (6) a fine dispersion of sodium in tetrahydrofuran is added to a mixture of pyrrolidone and tetrahydrofuran containing a little aluminium stearate and oleic acid; after evolution of gas has ceased, the solution is employed under conditions similar to those of (1) to prepare vinyl pyrrolidone. Other specified lactams for vinylation are caprolactam and 2-piperidone. According to the Provisional Specification the vinylation is effected at 110 DEG to 180 DEG C.