No abstract

The action of alkyl iodides on the Grignard derivatives of 2 : 3 : 4-and 2 : 3 : 5-trialkylpyrroles and 2 : 3 : 4 : 5-tetra-alkylpyrroles is shown to give tetra-and penta-alkyl-2H-pyrroles (pyrrolenines) containing 2 : 2-gemdialkyl groups. The reaction is inhibited by the presence of ester substituents on the pyrrole ring.ALTHOUGH the structure of the alkylation products of pyrroles caused a lengthy poleniic some forty years ago, the subject has scarcely received comment since. In spite of all the early work it is impossible, because of the conflicting claims, to predict the position of alkylation in pyrrole rings containing varying numbers of alkyl groups. Ciamician and Anderlini suggested 1 : 2-dihydropyridine structures for the base C,H,,N obtained by treating sodium pyrrole-2-carboxylate with methyl iodide in methanol and for the base Cl,Hl,N from l-methylpyrrole and methyl iodide in methanol in presence of potassium carbonate. Influenced by Plancher's work on the alkylation of indoles, Ciamician later suggested that the pyrrole alkylation products were more likely to be derivatives of 2H-pyrrole (pyrrolenine) and this was eventually substantiated by Plancher himself ,3 Me \ Me Mek-JEMFLJ;: R Me20::Me (111) Me (IV)although the dihydropyridine structures were still favoured by some authors* as late as 1914. The base C,H15N thus was recognised as a pentamethyl-2H-pyrrole or -3H-pyrrole although the precise location of the substituents was not established by Ciamician or Plancher, and Beilstein 5 gives the alternative structures, (I; R = Me) and ( 11), for the methylation product. However, in a related series, an unequivocal proof of structure was apparently obtained by Hess, Wissing, and Suchier who claimed that methylation of 3-ethyl-2 : 5-dimethylpyrrole gave the same product as was formed by ethylation of 2 : 3 : 5-trimethylpyrrole, thus suggesting that in a 2 : 3 : 5-trialkylpyrrole, further alkylation occurs a t the 3-(Le. 8-)position. It will be shown subsequently that the German experimental work was at fault and the conclusion incorrect.We have prepared the base C,H15N from methyl iodide and the Grignard derivatives

3‐Methylpentane‐2,4‐dione product: 3‐methylpentane‐2,4‐dione

2,3,4,5‐Tetramethylpyrrole product: 2,3,4,5‐Tetramethylpyrrole

tenophenanthrene from 2-[/3-halopropionyl] -phenanthrene were unsuccessful.3. Diels' hydrocarbon and its ethyl and isopropyl homologs were prepared from the corresponding 2-acylphenanthrene derivatives.4. Several intermediates and derivatives of the above compounds are described.Evanston, Illinois