Benzopyrans. Part-XXVIl. Synthesis of 2-Methyl-4-oxo- 4H-1-benzopyran-3-carboxaldehyde and 3(5)-Salicyloylpyrazole from 2-Unsubstituted 4-Oxo-4H-1- benzopyran-3-carboxaldehyde
| Main Authors: | CHANDRA KANTA GHOSH, SUBHABRATA BISWAS |
|---|---|
| Format: | Article Journal |
| Bahasa: | eng |
| Terbitan: |
, 1990
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/6218502 |
Daftar Isi:
- Organic Chemistry Laboratory, Department of Biochemistry, Calcutta University, Calcutta-700 019 Manuscript received 14 February 1990, accepted 30 March 1990 The fused 1-pyrazoline (3), prepared from diazomethane and the acetal (2) corres-ponding to 4-oxo-4H-1-benzopyran-3-carboxaldehyde (1; R=H,Me, Cl and Br) gives exclusively the acetal (4) on being refluxed in toluene but a mixture of the acetal (4) and 3(5)-salicyloylpyrazole (9) on neat pyrolysis at 160-70°. The pyrazole (9) also results exclusively from percolation of a solution of the pyrazoline (3) in ethyl acetate through a column of Brockman neutral alumina. Acid-catalysed deacetalisation of the acetal ( 4) affords the title aldehyde (5).