合成路线1

Alkylation of 2,4-dinitrothiophenol (I) with 2-bromoisobutyrate (II) and K2CO3 in DMF yields thioether (III), which is then subjected to reduction with Fe/HCl in EtOH/H2O, followed by ring closure with refluxing NaOH, to give benzothiazine derivative (IV). Conversion of amino compound (IV) into nitro derivative (V) is then performed via Sandmeyer reaction by first treatment with NaNO2/H2SO4 in H2O, followed by reaction with NaHCO3, NaNO2, CuSO4 and Cu2O in H2O. N-Alkylation of (V) with chloroacetone (VI) and K2CO3 in DMF provides (VII), which is finally converted into the target compound by reduction with BH3-THF complex in THF, followed by Swern oxidation with DMSO and oxalyl chloride in CH2Cl2.