Spiro[cycloalkane‐1,3′‐[3H]indoles] 2 can be obtained from the cycloalkanecarbaldehydes 1 by the Fischer reaction of their phenylhydrazones. These cyclizations are sensitive to the acid catalyst, solvent and temperature employed. Rearrangement of the 2 to the homologous cycloalkane derivatives 3 can occur by an acid catalyst or by thermal treatment of 2 in ethyleneglycol.
Tris(triphenylphosphine)nickel(O)(A) and a zerovalent pyridine-nickel complex (B) have been used as reagents for the coupling reaction of 3-, 6-and 8-bromoquinolines: 3,3'-, 6-6'-and 8,8'-Biquinolines were obtained in quantitative yields when A was used as the coupling reagent. B gave always a mixture of the n,n'-biquinoline and substitution products. A mechanism can be outlined to explain the coupling reaction of bromoquinolines using zerovalent nickel complexes.
The synthesis of 4‐vinylquinoline has been carried out by means of the Wittig reaction between 4‐quino‐linecarbaldehyde and the methyl triphenylphosphonium ylide in dimethyl sulphoxide in good yield. Dehydration of the 4‐(1‐hydroxyethyl)quinoline and their xanthate derivative, give equimolar amounts of 4‐ethylquinoline and 4‐acetylquinoline while small amounts of 4‐vinylquinoline were found. Dehydrochlorination of 4‐(1‐chloroethyl)quinoline in ethanol‐sodium hydroxide provides 4‐ethyl‐3‐ethoxyquinoline in good yield, but 4‐vinylquinoline is a minor reaction product.
1′‐Methylspiro[3H‐indole‐3,n'‐piperidines] 2 can be obtained from the 1‐methyl‐n‐piperidinecarbaldehydes 1 by the Fischer reaction of their phenylhydrazones. The Fischer reaction provides different kinds of products ‐3H‐indole, indole and oxindole‐ which depend on the N atom position in the piperidine ring.
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