- A New Synthetic Method for the 2-Substitution of N-Unsubstituted Benzimidazoles: Formaldehyde as a Versatile Protecting Agent for Heterocyclic NH
-
N-Unsubstituted benzimidazoles 1 are readily converted in a one-pot sequence into 2-substituted derivatives 2 with good overall yields.N-Protection with formaldehyde and lithiation with lithium N,N-diisopropylamide (LDA), n-butyllithium, or tert-butyllithium gives the dilithiohemiaminals 6, which readily react with a range of electrophiles at the 2-carbon.The 2-substituted 1-(lithioxymethyl)benzimidazoles 7 undergo smooth acid-catalyzed dehydroxymethylation under mild conditions to give N-unsubstituted 2-substituted benzimidazoles 2.
- Katritzky, Alan R.,Akutagawa, Kunihiko
-
p. 2949 - 2952
(2007/10/02)
-
- Practicable Syntheses of 2-Hydroxymethyl-substituted Benzimidazoles and 2-Formylbenzimidazole
-
N-Protection of benzimidazole by a diethoxymethyl group, as in , allows exclusive lithiation at the 2-position.This protected anion can be made to react with various electrophiles (e. g. ketones, aldehydes) to yield the corresponding 2-hydroxymethylbenzimidazoles (1).Facile deprotection occurs with acid.Two practicable syntheses of 2-formylbenzimidazole are also described and an indirect route to benzimidazole-2-alcohols is discussed.
- Ooi, Hong Chin,Suschitzky, Hans
-
p. 2871 - 2876
(2007/10/02)
-