Microwave‐Assisted Synthesis of 10‐(Phthalimidoalkyl)‐halosubstitutedpyrido [3,2‐b][1,4]‐benzothiazine in Dry Media

Abstract

N‐Alkylation of 10H‐9‐fluoropyrido[3,2‐b][1,4]‐benzothiazine 5a, 10H‐7‐fluoropyrido[3,2‐b][1,4]‐benzothiazine 5b, and 10H‐7‐chloropyrido[3,2‐b][1,4]‐benzothiazine 5c with different N‐(bromoalkyl)phthalimides using anhydrous K₂CO₃ and tetrabutylammonium bromide (TBAB) under dry conditions with microwave irradiation leads to the formation of 10‐(phthalimidoalkyl)‐halosubstitutedpyrido[3,2‐b][1,4]‐benzothiazine (6a–f) along with some unidentified product. Compound 5a is a new azaphenothiazine derivative and was obtained from hitherto unknown 2‐acetylamino‐3‐fluorophenyl‐3′‐nitro‐2′‐pyridylsulfide 4a via Smiles rearrangement. Compound 4a is required for the synthesis and has been prepared starting from 2‐amino‐3‐fluorobenzenethiol 1a in three steps.

Keywords:

• 2‐acetylamino‐3‐fluorophenyl‐3′‐nitro‐2′‐pyridylsulfide
• 10H‐9‐fluoropyrido[3,2‐b][1,4]‐benzothiazine
• 10‐(phthalimidoalkyl)‐halosubstitutedpyrido [3,2‐b] [1,4]‐benzothiazine
• Smiles rearrangement

Acknowledgment

The authors A. G. and R. S. are thankful to the Department of Science and Technology (DST) and the Council of Scientific and Industrial Research (CSIR), Government of India, New Delhi, for the Women Scientist Award and a senior research fellowship, respectively.