Investigations concerning the Synthesis of Condensed Furanopyrazoles, Furanodiazepines and Furanooxazepines starting with 3-Chloro-6-methoxybenzofuran- 2-carboxaldehyde. Part-IV

Department of Chemistry, Indian Institute of Technology, Madras-600 036
Manuscript received 4 August 1989, accepted 22 January 1990

3-Chloro-6-methoxybenzofuran-2-carboxaldehyde (2) on condensation with a variety of nitrogen dinucleophiles gave the expected aldimines (3a - d, 4a- d, 5). Attempted intramolecular cyclisation under the influence of acid or base catalysis or thermolysis or even photolysis of these aldimines (3a- d, 4a- d, 5) was however found to be unsuccessful. Even the chloroacetal (12) prepared from the chloroaldehyde (2) failed to undergo substitution of the halogen by the nitrogen nucleophiles in affording the corresponding substituted acetal (13). The tosylate (16) derived from the aldimine (5) also failed to undergo intramolecular cyclisation in furnishing the anticipated seven-membered heterocyclic derivative (17).