Intramolekulare Aromatenalkylierungen, XXXV: Di- und Tetrahydropyridinylmethylindoline als potenzielle Vorstufen zu Ergolinen

In the presence of methyl chloroformates compound 6a is reduced by NaCNBH 3 yielding the 1,6-dihydropyridine derivative 7. Under the same conditions the indoline 10 accessible from 6a via 9a gives a mixture of the 1,4- and 1,6-dihydropyridine derivatives 11 and 12. As by-product of the reduction the borane adduct 13 is detected. In contrast the methoiodide 1 is reduced by NaBH 4 or DIBAH giving a separable mixture of the diastereomers of the tetrahydropyridines 2 and 3; on catalytic hydrogenation the piperidine derivative 4 is formed. Cleavage of the enolether moiety in 3a and 7 provides the corresponding piperidones 5 and 14, respectively. Using prolonged reaction time 7 is hydrolized quantitatively furnishing the 1,4-diketone 15.