Regioselective Azidation of 2,4-Dichloroquinolines

Abstract

Reactions of 2,4-dichloroquinolines (2a–f) with sodium azide in DMF lead either regioselectively to 4-azido-2-chloroquinolines (3a–f) or with excess of sodium azide and catalysts to 5-azido-tetrazolo[1,5-a]quinolines (4a–f). 2,4-Dichloroquinolines (2g–i) having electron donating substituents in 3-position react with sodium azide in DMF to a mixture of 4-azido-2-chloroquinolines (3g–i) and 5-chlorotetrazolo[1,5-a]quinolines (5g–i). When the reaction of the 2,4-dichloroquinolines (2a–i) with sodium azide is carried out in ethanol with addition of methanesulfonic acid, regioselectively 5-chloro-tetrazolo[1,5-a]quinolines (5a–i) are obtained. Structural assignments of 3 and 5 have been carried out by 13C-NMR spectra, IR spectra and degradation reactions of the azido- and tetrazolo group to aminoquinolines (7 and 10) via iminophosphoranes (8 and 9). It could be shown that in 2-azido/tetrazolo-quinolines (4 and 5) the tetrazole ring structure is the dominant species.