Iminium carbonic acid derivative salts. X. Synthesis of N,S‐containing heterobicycles from N‐protected 2‐methylthio‐1,3‐thiazinium and 2‐methylthiothiazolium salts. Part 2. Reaction of N‐protected 2‐methylthio‐1,3‐thiazinium and 2‐methylthiothiazolium salts with vinylogous CH‐acidic compounds

• Published in: Journal of Heterocyclic Chemistry
• Main Authors: Hanefeld, Wolfgang, Naeeni, Mahmoud, Schlitzer, Martin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Ketene; Carbonic acid
• Online Access: http://dx.doi.org/10.1002/jhet.5570330640; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjhet.5570330640; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jhet.5570330640

Abstract N ‐Boc‐protected 2‐methylthio‐1,3‐thiazinium 3 and 2‐methylthiothiazolium salts 4,7 obtained from the corresponding 1,3‐thiazine‐2‐thiones and thiazolidine‐2‐thiones by the action of methyl iodide or trimethyloxonium tetrafluoroborate were reacted with vinylogous CH‐acidic compounds forming ketene N,S ‐acetals 5,6,8,9 . The protection group was removed with trifluoroacetic acid whereupon the desired cyclisation to pyrido[2,1‐ b ]‐1,3‐thiazines 10 and thiazolo[3,2‐ b ]pyridines 11,12 took place.