An Investigation of the Reaction of 2-Aminobenzaldehyde Derivatives with Conjugated Nitro-olefins: An Easy and Efficient Synthesis of 3-Nitro-1,2-dihydroquinolines and 3-Nitroquinolines

2-Aryl-3-nitro-1,2-dihydroquinolines 3 were prepared from the reaction of β-nitrostyrenes 2 and 2-aminobenzaldehyde 1 in the presence of DABCO. Not only β-nitrostyrenes but other alkyl nitro olefins also can be used in this reaction as well. When DDQ or silica gel was added to a solution of 3-nitro-1,2-dihydroquinolines 3, 3-nitro-2-substituted-quinolines 4 were obtained. When 2-aminobenzaldehyde derivatives 7 and 12 were reacted with β-nitrostyrenes 2, unique rearrangement products were produced.