Scheme 2. Syntheses of N-Acyl BITs 4a and 4b and O-Acyl Benzisothiazolols 5a and 5b.
Reagents and conditions: (i) CuI, 1,10-phenanthroline, sulfur, K2CO3, DMF, 110 °C, overnight; (ii) piperidine-1-carbonyl chloride (a) or (S)-2-methyl-1,4-dioxa-8-azaspiro[4.5]decane-8-carbonyl chloride (b), pyridine, CH2Cl2, rt, 24 h.