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A facile synthesis of 4‐, 6‐ and 7‐formyl‐1 H ‐indole‐2‐carboxylates: The CH 2 SO 3 H functionality as a masked formyl group
Author(s) -
Pete Béla,
Szokol Bálint,
Szöllőy Áron
Publication year - 2006
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.5570430528
Subject(s) - chemistry , indole test , yield (engineering) , hydrolysis , methanesulfonic acid , hydroxymethyl , medicinal chemistry , organic chemistry , stereochemistry , metallurgy , materials science
The valuable new synthetic intermediates, ethyl 4‐, 6‐ and 7‐formyl‐1 H ‐indole‐2‐carboxylates ( 10, 11, 12 ) were prepared from 2‐ethoxycarbonyl‐1 H ‐indole‐4‐, 6‐ and 7‐methanesulfonic acids ( 1, 2, 3 ), respectively. The transformation of sulfomethyl group to formyl function was accomplished through elimination of SO 2 to yield ethyl 4‐, 6‐ and 7‐chloromethyl‐1 H ‐indole‐2‐carboxylates ( 4, 5, 6 ), hydrolysed to ethyl 4‐, 6‐ and 7‐hydroxymethyl‐1 H ‐indole‐2‐carboxylates ( 7, 8, 9 ), then oxidized to aldehydes ( 10, 11, 12 ). Protection at N1 of indole was not necessary. A marked increase in the rate of hydrolysis of 7‐chloromethyl‐indoles compared to that of 4‐ and 6‐(chloromethyl)indoles was observed.