A Facile Synthesis of 1-Substituted 3-Alkoxy-1<i>H</i>-isoindoles Based on the Reaction of 2-(Dialkoxymethyl)phenyllithiums with Nitriles, Followed by Acid-Catalyzed Cyclization
作者:Minami Kuroda、Kazuhiro Kobayashi
DOI:10.1002/hlca.201400333
日期:2015.3
A two‐step synthesis of 1‐substituted 3‐alkoxy‐1H‐isoindoles 4 has been developed. Thus, the reaction of 2‐(dialkoxymethyl)phenyllithium compounds, which are easily generated in situ by Br/Li exchange between 1‐bromo‐2‐(dialkoxymethyl)benzenes 1 and BuLi in THF at −78°, with nitriles afforded [2‐(dialkoxymethyl)phenyl]methanimines 2, which were treated with a catalytic amount of TsOH⋅H2O in refluxing
Irradiation of 4-azidoisoquinolines (1a-e) in the presence of sodium methoxide resulted in ring-expansion to give 5-methoxy-1H-2, 4-benzodiazepines (10) : the structures of the products were confirmed by the following chemical studies as well as spectral analyses. Treatment of the diazepines (10) with hydrochloric acid or acidic alumina in methanol resulted in ring-contraction to afford 1-aminoisoindolenines (14), and treatment with acetic anhydride gave the ring-opened products (16). The diazepines (10) were also converted to 1-methoxyisoindolenines (19) by further irradiation and to the diazepin-3-one (21) by treatment with either mesitylnitrile oxide or lead tetraacetate.