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Synthesis and reactions of lithio derivatives of 1‐allenylbenzotriazole
Author(s) -
Katritzky Alan R.,
Verin Sergei V.
Publication year - 1995
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.5570320153
Subject(s) - lithium diisopropylamide , chemistry , benzophenone , allene , acetone , metalation , lithium (medication) , yield (engineering) , ketone , organic chemistry , medicinal chemistry , transmetalation , deprotonation , catalysis , ion , medicine , materials science , metallurgy , endocrinology
1‐(2‐Chloropropen‐2‐yl)benzotriazole ( 6 ) is converted by heating with sodium hydroxide or by lithium diisopropylamide at ‐78° into 1‐allenylbenzotriazole ( 1 ) in high yield. Allene 1 undergoes in situ lithiation at the α‐carbon and subsequent reactions with iodomethane or carbonyl compounds to produce 1‐(1‐substituted allenyl)benzotriazoles 9 and 2a‐c , respectively. Three equivalents of lithium diisopropylamide dilithiated 1 and afforded symmetrical 1‐(1,3‐disubstituted allenyl)benzotriazoles 11a,b upon reaction with ketones. The unsymmetrical 1‐(1,3‐disubstituted allenyl)benzotriazole 5 was obtained via a stepwise addition of benzophenone to the lithio derivative of 1 followed by a second lithiation and quenching with acetone. Monosubstituted allenes 2a and 8 were cyclized into the benzotriazolyl substituted dihydrofuran 3 and dihydropyrrole 4 respectively.