Regioselective Azidation of 2,4-Dichloroquinolines

Article abstract of DOI:10.1002/prac.19943360407

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.