A method for the preparation of certain isomers of 1 - (4 - bromophenyl) - 1 - (2 - pyridyl) - 3 - pyrrolidino - propene - (1) and of 1 - (5 - chlorine - 2 - thienyl) - 1 - (2 - pyridyl) - 3 - pyrrolidino - propene - (1)

摘要

The invention comprises 1-(41-bromophenyl)-and 1 - (51 - chloro - 21 - thienyl) - 1 - (211 - pyridyl) - 3 - pyrrolidinoprop - 1 - ene (and their salts) in the form of the geometrical isomers which exhibit an ultra-violet absorption spectrum similar to that of pyridylethylene, and the preparation thereof by dehydrating the corresponding carbinol and, if necessary, separating the required isomer from the other. It is possible to carry out the dehydration under such conditions that the required isomer is produced substantially exclusively, e.g. by drastic methods involving the use of sulphuric acid of high concentration, prolonged heating, high temperatures or a combination of two or all of these. Under milder conditions, e.g. by heating with 80 per cent sulphuric acid on a steam bath for 10 minutes, a mixture of isomers is obtained and may be separated by fractional crystallization of the base or a salt (e.g. the oxalate) thereof, chromatography on a column of alumina or a base-exchange resin, or removal of the undesired isomer by degradation with boiling acetic anhydride. The products possess anti-histamine activity. In examples: (1) (a) 1 - (41 - bromophenyl) - 1 - (211 - pyridyl) - 3 - pyrrolidinopropan - 1 - ol is heated with 85 per cent. sulphuric acid at 180 DEG C. for 10 minutes and the mixture of isomers formed is separated by crystallization from light petroleum or chromatography on an alumina column; (b) the dehydration is effected with 98 per cent. sulphuric acid under otherwise identical conditions, yielding the desired isomer almost exclusively; (2) (a) 1-(51-chloro-21-thienyl) - 1 - (211 - pyridyl) - 3 - pyrrolidinopropan-1-ol is heated with 65 per cent. sulphuric acid at 105 DEG C. for 10 minutes and the mixture of isomers is separated by base-exchange chromatography on a column of sulphonated cross-linked polystyrene; (b) the dehydration is effected with 85 per cent. sulphuric acid, yielding the desired isomer almost exclusively. Specifications 685,696 and 689,234 are referred to. The Provisional Specification does not make any distinction between the geometrical isomers of the products. 1 - (41 - Bromophenyl) - and 1 - (51 - chloro - 21 - thienyl) - 1 - (211 - pyridyl) - 3 - pyrrolidinopropan-1-ol are prepared by the action of 2-pyridyl lithium on, respectively, p-bromo-b -pyrrolidinopropiophenone and 5-chloro-2-thienyl-b -pyrrolidinoethyl ketone, which are obtainable by the Mannich reaction from p-bromoacetophenone and 2-acetyl-5-chlorothiophen respectively.