Mechanistic investigations by means of proton spectroscopy substituted (8a, b) and 1,2-disubstituted pyrroles (8c-i), respectively. The 3-substituted secondary trans-detected intermediates and uncovered the course of reactions in acetate-buffered [D 4 ]methanol of primary cyclopropanediammonium dibromides 24โข2HBr furnish 1,2,4trisubstituted pyrroles 25. While the primary 1-cyclopropanediamines cis-and trans-2a with benzaldehyde (3a) or 2,2-dimethylpropanal (3b), of secondary cyclopro-methylcyclopropanediammonium dibromide trans-14aโข2HBr reacts regioselectively with 3a and c to produce only 2,3-panediamines cis-and trans-2b with 3b, and of the ringmethylated cyclopropanediamine trans-14a and the aromatic substituted pyrroles 19a, c, the corresponding secondary dibromide trans-14cโข2HBr gives rise to the formation of aldehydes 3a and c. This study provided the basis of an expedient synthesis of pyrroles which takes place under mixtures of 1,2,3-( 22) and 1,2,5-trisubstituted pyrroles 23.
The key step of pyrrole formation from 1,2-cyclo-exceptionally mild conditions. Irrespective of the configuration, primary (2aโข2HBr) and secondary propanediamines and aldehydes is the ring expansion of intermediate monoiminium ions of type 5 via azomethine cyclopropanediammonium dibromides 2b and cโข2HBr that are devoid of ring substituents react with aromatic aldehydes ylides (E,Z)-6 to yield dihydropyrrolium ions 7. 3a, e-h, cinnamic aldehyde (3i), and 3b to afford 2- [แญ] Part 6: Ref. [2] . The results are part of the dissertations by J.