Premium
Dimerizations of 2‐Alkylbenzotriazoles and Chemical Evidence of Radical Intermediates from X‐ray Studies
Author(s) -
Katritzky Alan R.,
Jesorka Aldo,
Wang Jin,
Yang Baozhen,
Wu Jing,
Steel Peter J.
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960517
Subject(s) - chemistry , benzophenone , benzotriazole , lithium diisopropylamide , adduct , medicinal chemistry , benzaldehyde , nucleophilic addition , nucleophile , stereochemistry , photochemistry , organic chemistry , ion , deprotonation , catalysis
Treatment of 2‐alkylbenzotriazoles with lithium diisopropylamide (LDA) at −78°C gave, depending on workup conditions, either dimers of the type Bt 2 CHRCHRBt 2 ( 2 ) (Bt 2 = benzotriazol‐2‐yl), or mixtures of symmetrical Z and E olefins ( 3 ) (RCHCHR), in high yields via radical intermediates. The racemic and meso isomers of 2 , which differ substantially in properties such as melting points, 1 H and 13 C NMR, were isolated and characterized (three by X‐ray crystallography). Both the meso and racemic dimers of 2 were reduced by Na to give mixtures of Z and E olefins in high yields with the elimination of the benzotriazole anion. 2‐Alkylbenzotriazoles ( 1 ) were also converted by Na into the corresponding alkanes and benzotriazole. The intermediates were trapped by benzophenone to give, depending on the reaction procedure (see Scheme 2), adducts 6 or adducts 6 with dimers 2 , benzotriazol‐2‐ylalkene 7 and compound 8 (R H), compound 9 (R CH 3 ). Several compounds with dibenzotriazol‐2‐yl groups or benzotriazol‐1‐yl and benzotriazol‐2‐yl groups in the same molecule were synthesized and further investigated via lithiation followed by the addition of benzophenone or benzaldehyde. This further indicated that the radical reaction is faster than the nucleophilic reaction.