- AN UNEXPECTED RING-OPENING IN THE REISSERT REACTION ON 2,3-DIPHENYLQUINOXALINE-N-OXIDE.
-
When quinoxaline-N-oxide 1 is reacted with KCN and benzoyl chloride in water (the Reissert reaction) or methanol, the products are 2-, 5- and 6- chloroquinoxaline (the latter being the major product: 42+/-6percent) and small amounts of 2-cyanoquinoxaline.Using three equivalents of trimethylsilyl cyanide instead of KCN, and dichloromethane as the solvent, leads to a 72percent yield of 2-cyanoquinoxaline.The reaction of trimethylsilyl cyanide and benzoyl chloride with 2,3-diphenylquinoxaline-N-oxide 2 leads to an unexpected ring-opening product 13; its structure is based on spectroscopic data and on an X-ray crystallographic analysis.
- Nasielski, J.,Heilporn, S.,Nasielski-Hinkens, R.,Tinant, B.,Declercq, J. P.
-
p. 7795 - 7804
(2007/10/02)
-
- REGIOSELECTIVITY IN THE REACTION OF NITROQUINOXALINE-N-OXIDES WITH PHOSPHORYL CHLORIDE
-
6-nitro-, 2-methyl-6-nitro- and 2,3-dimethyl-6-nitroquinoxaline have been transformed into their N-oxides by MCPBA in chloroform; the nitro group orients the oxygen atom preferentially to nitrogen atom N1, but the N4:N1 selectivity is diminished in the methylated derivatives.Under the action of POCl3 (the Meisenheimer reaction), the N-oxides of the unmethylated compounds are transformed into chloro-nitroquinoxalines having lost the N-oxide oxygen atom.The orientation of the entering chloride ion is discussed on the basis of electronic effects induced by the N-oxide and nitro groups, and it is suggested that the last step, the elimination of "HPO2Cl2" is a concerted process.
- Nasielski-Hinkens, R.,Vyver, E. Vande,Nasielski, J.
-
p. 663 - 670
(2007/10/02)
-
