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Sulfenylation of some pyrroles and indoles
Author(s) -
Gilow Helmuth M.,
Brown Christopher S.,
Copeland John N.,
Kelly Keith E.
Publication year - 1991
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570280432
Subject(s) - chemistry , morpholine , electrophilic substitution , oxidizing agent , pyridine , electrophile , medicinal chemistry , alkyl , catalysis , electrophilic aromatic substitution , chloride , organic chemistry
Methylsulfenylation of 1‐substituted pyrroles and indoles was observed using 1‐(methylthio)morpholine and an acid catalyst or with methylsulfenyl chloride and excess pyridine. 1‐Substituents which are activating or weakly deactivating towards electrophilic substitution such as alkyl, 2‐cyanoethyl, dimethylamino, trialkylsilyl, 2‐chloroethyl and 2‐phenylsulfonylethyl were used. The 2‐chloroethyl and 2‐phenylsulfonylethyl groups which can be removed with a strong base can be used to obtain 1 H ‐methylthiopyrroles and indoles. 1‐Phenylsulfonyl and 1‐acetyl substituents are too strongly deactivating for these sulfenylations to be successful. Mono and disubstituted pyrroles and monosubstituted indoles can be isolated from these reactions, however, because the methylthio group is activating towards electrophilic substitution the main advantage of these reactions is the synthesis of tri and tetrasubstituted pyrroles and disubstituted indoles. 1‐Methyl‐2,3,4,5‐tetra‐methylthiopyrrole and 1‐methyl‐2,3‐dimethylthioindole are oxidized to the corresponding 3,4‐disulfoxide and 3‐sulfoxide and with excess oxidizing agent to the tetrasulfone and disulfone, respectively.