Mono- and Dialkylations of Pyrrole at C2 and C5 Positions by Nucleophilic Substitution Reaction in Ionic Liquid

Abstract

[reaction: see text] A novel ionic liquid methodology for pyrrole C-alkylation is described. The pyrrole alkylation is achieved with various simple alkyl halides and mesylates selectively at C2 and C5 positions in good yields with minimal byproducts under relatively mild conditions in various ionic liquids. 2-(3-Phenylpropyl)pyrrole (2a) was synthesized from pyrrole and 1-bromo-3-phenylpropane in a mixture solvent system, [bmim][SbF6] and CH3CN, in 81% yield at 115 degrees C for 44 h with 5% yield of dialkylated compound 3a.

Regioselective Alkylation of an Oxonaphthalene-Annelated Pyrrol System

“…Since the pyrrole derivative 1 is in conjugation with a strongly electron-withdrawing carbonyl group, previously published studies (see below) on C-vs. N-alkylation of pyrrole are not fully comparable and thus cannot give a clear explanation of these results: K. Sukata had described increasing C-alkylation vs. N-alkylation of pyrrole in protic solvents such as PEG or water, in aprotic solvents such as PEG-ethers N-alkylation was preferred [10]; D. Y. Chi had developed an ionic liquid methodology for pyrrole to achieve regioselective N-and C-alkylation, respectively [11,12]. After cleavage of the N-BOC protecting group, both compounds will now serve as starting materials for the syntheses of new anticancer drugs with a nitrogen mustard moiety, the results will be reported elsewhere.…”

Synthesis of Selectively 13C‐Labelled Bilin Compounds

“…The crucial FULL PAPER step in this reaction sequence was then the alkylation of a pyrrole at a free α-position. Only two possible procedures were known -either by following a radical mechanism [12,13] or by performing the reaction in ionic liquids [14,15] -but both of these turned out to be inefficient for the synthesis of an all-carbon-substituted pyrrole, due to low yields. Nonetheless, we introduced benzyl [2-…”

Environmentally benign and highly regioselective ring opening of epoxides accelerated by ultrasound irradiation

“…Due to the nucleophilic nature of indoles and imidazoles and versatile usage of these compounds in medicine and biochemistry, various methods have been developed for alkylation of these compounds (20,21 (29), activated silica (30) and high-pressure conditions (31). While such methods have expedited alkylation of nitrogen heterocycles, they showed varying grades of success as well as limitations such as prolonged reaction times, low yields, use of toxic solvents and expensive catalysts.…”