ISSN:
0170-2041
Keywords:
Acetal ring closure
;
Aldol ring closure
;
Quinolizinium salts
;
Bicyclo[3.3.1]nonadiene
;
Pyridone methides
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
3-Acetyl-7,12-dihydro-2-methyl-6H-indolo[2,3-a]quinolizinium chloride (1) forms “dimers” (5a, b) by condensation with benzaldehyde and by means of kinetically controlled acetal ring closure (piperidine catalysis). In 5a, b the two quinolizinium units are connected by intercalation of a hydrogenated chroman system whose reactivity is attributed to the presence of a pyranoid hemiacetal structure. On standing or heating of their solution 5a, b are converted via the intermediate 4 and aldol ring closure into the thermodynamically more stable diastereoisomers 2a, b with a bicyclo[3.3.1]nonadiene system. All the ring closures occur with diastereofacial selectivity. In the case of the condensation of 1 with salicylaldehyde the Schiff base of this aldehyde with aniline replaces the aldehyde moiety as well as the piperidine catalyst and yields 10a, b under kinetically controlled conditions. By sodium tetrahydridoborate reduction in methanol 5a is converted into 7, the X-ray structural analysis of which confirms structure and stereochemistry.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1992199201208
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