- New route of benzyne cyclization for synthesis of 2,3,4,5-tetrahydro-1h-pyrido[4,3-b]indole derivatives avoiding highly toxic aryl hydrazines
-
A new route for the regioselective synthesis of 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole derivatives was developed based on cyclization of 3-chlorophenylimine-N-alkyl-4-piperidones by "the complex bases" of NaNH2 or KNH2. The procedure was performed under variable reaction conditions in inert proton-free solvents, such as THF, dioxane, 1,2-dimethoxyethane, toluene, and xylene, at temperatures varying from 20C to boiling point of the solvent used. Toxic arylhydrazine intermediates occurring in the classical Fischer indole synthesis are avoided.
- Kovacikova, Lucia,Stefek, Milan
-
p. 1257 - 1263
(2015/04/27)
-
- PROCESS FOR THE PREPARATION OF 2,3,4,5-TETRAHYDRO-1H-PYRIDO[4,3-B]INDOLE DERIVATIVES
-
The value of the invention is the application of the cyclization of Schiff-bases of the general formula (3a-i), where R1 - R8 are substituents defined in example 1, whereby R9 = Cl using complex bases of amides of group I of the periodic table (NaNH2, KNH2) from 2.1 - 5 equiv. and alcoholates of group I of the periodic table (t-BuONa, tBuOK) from 0.05 - 2 equiv. with the advantage of application of 3 equiv. of NaNH2 and 0.05 equiv. of t-BuONa, or their mixtures with PEG (m.w. = 500 - 6000), or crown ethers, or catalysts of phase transfer lithium in inert proton-free diluents, such as benzene, cyclohexane, toluene, xylene, 1,2-dimethoxyethane, dioxane, etc., with the advantage of using THF, at a temperature from 20 °C to boiling point of the diluent used, or with the application of organo-metallic bases such as LDA, t-BuLi in inert proton-free diluents at a temperature from -80°C to 25 °C.
- -
-
Page/Page column 13-14
(2011/11/30)
-