Abstract
A series of 3-(aminomethylene)-3H-indoles (1a-e and 6a-8a) was prepared by the condensation of 3-indolecarbaldehydes (2-5) with secondary amines. Among them, 3-(1-pyrrolidinylmethylene)-3H-indoles (1a and 6a-8a) were obtained as stable colorless prisms, while 3-(piperidinomethylene)-3H-indole (1b) and 3-(morpholinomethylene)-3H-indole (1c) readily polymerized in refluxing benzene. Reaction of 1 with electrophiles, such as alkyl and acyl halides, gave 1-substituted 3-aminomethylene-3H-indolium salts, which were converted to the corresponding 1-substituted 3-indolecarbaldehydes by hydrolysis. Reaction of 1 with active methylene compounds proceeded under mild reaction conditions to afford the corresponding condensation products in good yields. Successive reaction of 1 with electrophiles and nucleophiles provided a convenient route to 1, 3-disubstituted indole derivatives.
