Benzazoles and naphthazoles

A single‐step preparation of thiazolo[5,4‐b]pyridine‐ and thiazolo[5,4‐c]pyridine derivatives from chloronitropyridines and thioamides, or thioureas

“…A number of methods to prepare thiazolo[5,4‐ b ]pyridines have been documented in the literature [1]. For example, methods that construct the bicycle by formation of a thiazole ring, include condensations of 3‐amino‐2‐halopyridine, or 3‐amino‐2‐pyridone derivatives, with thiocyanates, thioamides, or thioesters [14], the oxidative ring‐closure of 3‐aminopyridine thioamides or thioureas [15], condensations with 3‐aminopyridin‐2‐thiones [16], and reactions of N ‐(2‐pyridone‐3‐yl)acetamides with phosphorous pentasulfide [17]. Recently, a cross‐coupling/cyclization sequence starting from N ‐(2‐bromopyridin‐3‐yl)acetamide was also detailed [18].…”

“…1) [19]. In contrast to many literature methods of thiazolopyridine synthesis, our method does not use reagents such as tin(II) chloride, thiocyanate salts, thiophosgene, organometallics, or bromine [14–18].…”