ISSN:
0947-3440
Keywords:
Chelation control
;
Lewis acid catalysis
;
Hetero Diels-Alder reactions
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Lewis acid-catalyzed cyclization of proline-derived N-arylimines 8 gives the tetracyclic decahydro-7,7,11-trimethyl-in-dolizino[3,4-b]quinolines 17a, b in a ratio, which is highly dependent on the coordination number of the acidic catalyst. Whereas monodentate Brønsted and Lewis acids as well as octahedral bidentate Lewis acids preferably gave the all-trans product 17b, the all-cis product 17a was obtained by tetrahedral aluminium Lewis acids. In contrast to this chelation-controlled reversal of diastereoselectivity, mixtures of cis/trans undecahydro-6,6,10-trimethyl-11-azacyclopenta[a]-anthracenes 18b-e, h were isolated from the cyclization of the corresponding cyclopentane-derived N-arylimines 16 irrespective of the Lewis acid. Force field calculations support a stepwise iminium ion cyclization under thermodynamic control rather than a concerted hetero-Diels-Alder mechanism.
Additional Material:
3 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1995199506140
