Abstract
An efficient method for the exclusive one-pot synthesis of novel pyrazolo (4,3-c)(1,5)- benzothiazepines (7a-e) possessing a spiro-3H-indoline nucleus is described. The investigation of the reaction between substituted o-aminothiophenols (5a-e) with 3-pyrazolidinyl-2H-indol-2- one (3) to form the title products has been found interesting in view of the fact that different reaction sites are available in the key intermediate 3 which may lead to a mixture of products. Conventionally, 3 did not undergo reactions with 5a-e even under drastic conditions of prolonged reflux using strong acidic or basic catalysts in high boiling organic solvents for many days. However, the exclusive formation of the title products in a satisfactory yield (71 %) was achieved under microwave irradiation coupled with various inorganic supports indicative of a very strong specific microwave effect.
Highlights
The 1,5-benzothiazepine class of compounds are important as calcium channel blockers of proven utility such as Diltiazem and those in which the fused benzene ring is substituted at various positions have been found to have enhanced pharmacological properties.[1]
For the aforementioned reasons and in a continuation of our search for better and improved cardiovascular drugs,[19] we investigated the synthesis of novel spiro [indole-pyrazolo[4,3-c][1,5]benzothiazepines] with the assumption that the incorporation of more than one bioactive heterocyclic moiety into a single framework may result into the production of novel heterocycles with enhanced bioactivity
The IR spectra of the products 7a-e did not reveal the presence of primary amino group as two bands in the region 34503150 cm–1 were absent
Summary
The 1,5-benzothiazepine class of compounds are important as calcium channel blockers of proven utility such as Diltiazem and those in which the fused benzene ring is substituted at various positions have been found to have enhanced pharmacological properties.[1]. No reaction was found to occur between 3 and 5a-e even on extended reflux for many days in organic solvents with strong acidic or basic catalyst (toluene + TFA, ethanol + HCl, piperidine).
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