Synthesis of quinoxalines or quinolin-8-amines from N-propargyl aniline derivatives employing tin and indium chlorides.
Pyrazino compounds such as quinoxalines are 1,4-diazines with widespread occurrence in nature. Quinolin-8-amines are isomerically related and valuable scaffolds in organic synthesis. Herein, we present intramolecular main group metal Lewis acid catalyzed formal hydroamination as well as hydroarylation methodology using mono-propargylated aromatic ortho-diamines. The annulations can be conducted utilizing equal aerobic conditions with either stannic chloride or indium(iii) chloride and represent primary examples for main group metal catalyzed 6-exo-dig and 6-endo-dig, respectively, cyclizations in such settings. Both types of reactions can also be utilized in a one-pot manner starting from ortho-nitro N-propargyl anilines using stoichiometric amounts SnCl2·2H2O or In powder. Mechanistic considerations are presented regarding the substituent-depending regioselectivity.
Institute of Organic Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria. wolfgang.schoefberger@jku.at.
Stefan
S
Aichhorn
Markus
M
Himmelsbach
Wolfgang
W
Schöfberger
D000814:Aniline Compounds / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D007204:Indium / Q000737:chemistry*; D015394:Molecular Structure; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry; D011810:Quinoxalines / Q000138:chemical synthesis* / Q000737:chemistry; D013329:Structure-Activity Relationship; D017971:Tin Compounds / Q000737:chemistry*
D000814:Aniline Compounds; D011804:Quinolines; D011810:Quinoxalines; D017971:Tin Compounds; D007204:Indium; C023599:stannous chloride; C020758:indium trichloride; C023650:aniline