[Reaction of 3-aryl-2-nitroacrylates with titanium tetrachloride. Formation of 4H-1,2-oxazines and hydroxy-arylaldehydes].
The reaction of ethyl 3-aryl-2-nitroacrylate (1a: aryl = 3-methoxyphenyl) with toluene in the presence of titanium tetrachloride gave 4-(4'-methyl-phenyl)-4H-1,2-benzoxazine (3) in a 44.2% yield. The acrylate 1a reacted with dichloromethane in the presence of titanium tetrachloride to give 5-methoxy-salicylaldehyde (2a) in a 61.8% yield. Therefore, 2a was presumed to be formed via an intermediate 4H-1,2-benzoxazine (3'), followed by ring opening to quinone methide and cyano formate. In a similar reaction using both toluene and dichloromethane, 1 bearing a 2-naphthyl group gave a dimer of quinone methide and 1-hydroxy-2-naphthaldehyde via 4H-naphth[2,1-e]-1,2-oxazine, respectively.
Hirotani
S
S
School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
Zen
S
S
D000179:Acrylates; D000447:Aldehydes / Q000138:chemical synthesis*; D055598:Chemical Phenomena; D002621:Chemistry; D010078:Oxazines / Q000138:chemical synthesis*; D014025:Titanium
D000179:Acrylates; D000447:Aldehydes; D010078:Oxazines; C025096:titanium tetrachloride; D014025:Titanium