ISSN:
0009-2940
Keywords:
Imines
;
Indolizidines
;
Quinolizidines
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Lewis acid-catalyzed cyclization of prolinal and 2-piperidine-carbaldehyde benzylimines 11, 12 results in the diastereoselective formation of α-amino-β-alkyl-substituted indolizidines 15, 17, 19, 21 and -quinolizidines 16, 18, 20, respectively. Both diastereoselectivity and constitution depend on the Lewis acid. FeCl3 yields α,β-trans-α-(benzylamino)-β-isopropenyl derivatives 15 and 16, probably by a cationic cyclization via carbenium ions 32a, b. In contrast, TiCl4 yields α,β-cis-α-(benzylideneamino)-β-isopropyl derivatives 19 and 20 by a novel cyclization/intermolecular hydride transfer mechanism, which was supported by deuterium labeling studies. Compounds 15, 16, 19, and 20 were converted to the diastereomeric acetamides 24, 25 and 28, 29. By an analogous cyclization of the aldehydes 8 and 9 only α,β-cis-α-hydroxy-β-isopropenylindolizidines 51 and -quinolizidines 52 were obtained irrespective of the Lewis acid used. The structures of 30 and 52 were elucidated by X-ray analysis.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19941271027
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