A novel ring transformation of 5-azidothiazoles

Theoretical Studies on N–O or N–N Bond Formation from Aryl Azide Catalyzed by Iron(II) Bromide Complex

“…An attempt to locate such a stepwise transition state was not successful, and only TS (1–2)A was obtained. About the concerted mechanism, our calculations are consistent with the thermolysis of aryl azides in previous reports, which described a concerted loss of N 2 and ring closure. − …”

Synthesis of condensed thiazoles. (Review)

“…On heating intramolecular cyclization occurs at the azido and acyl functions, leading to the formation of the isoxazolothiazole 29 with a yield of 50% [28]. The oxazole 30 is formed as side product.…”

“…d]thiazoles 91 were obtained from trans-alkenylazidothiazole 90 by heating in toluene with an overall yield of 40%, calculated on the initial thiazole 89[28…”

Recent Advances in Ring Transformations of Five-Membered Heterocycles and Their Fused Derivatives

“…The reaction proceeds by a nucleophilic ring opening at the CϪO bond to form the supposed intermediate 14, which undergoes ring closure to the final product. [11] The thermolysis was carried out in chloroform at 50°C for 4Ϫ36 h to afford the products in fair to good yields. According to a suggestion of the authors, the NϪO bond of the isoxazole ring was cleaved first upon the attack of the nucleophile to yield Some azidothiazoles 19 were found to undergo ring transformation to oxazoles and imidazoles 20 (X ϭ O or NPh) upon heating (Scheme 3).…”

“…Dehaen et al reported [11,39] a reaction of 5-azidooxazole-4-carboxaldehyde 63 to 4-oxazolylcarboxylic azide 64. The reaction is supposed to proceed by a Cornforth rearrangement (Scheme 8).…”