STEREOCHEMISTRY AND X-RAY CRYSTAL-STRUCTURE OF PYRROLE TRIMER - SYNTHESIS OF CIS-2,5-DI(PYRROL-2-YL)PYRROLIDINE (CIS PYRROLE TRIMER) AND X-RAY CRYSTAL-STRUCTURE OF THYLPHENYLSULFONYL)-2,5-DI(PYRROL-2-YL)PYRROLIDINE (MONOTOSYL CIS PYRROLE TRIMER)

Pyrrole reacts with aqueous hydrochloric acid at 0 degrees C to give a 2:1 mixture of trans(1) and cis(2) isomers of 2,5-di(pyrrol-2-yl)pyrr olidine which, by conversion into a mixture of the corresponding monot osyl derivatives then exposure of these to sodium hydroxide under phas e-transfer conditions, are converted completely into the tosyl derivat ive (4) of the cis isomer, from which the tosyl group can be cleaved t o produce pure cis 'pyrrole trimer'.