ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The possibility of preparing cycloalkanones with an asymmetric β-C-atom by enantiotopically differentiating retro-Claisen reactions of bicyclic diketones a (Scheme l) is tested with the decalin-1,8-diones 1 and 7, as well as with the bicyclo[3.3.0]octane-2,8-diones 10 and 11. Treatment of the reactive dione 1 with chiral tetra-alkyl titanate catalysts results in a low optical induction (13%, Scheme 2). Cleavage with the Nasalts of a-amino-alcohols and hydrolysis of the resulting amides or esters gives much better optical yields, reaching 86% ee with dione 1 and (-)-ephedrine (Scheme 3). Almost as efficient is N-methylephedrine with 75% optical induction (Scheme 5). Lower enantiotopical differentiation is, however, observed with (-)-ephedrine and diones 7 (44% ee), 10 (8% ee), and 11 (48% ee) (Schemes 3 and 4, Table l), or with dione 1 and L-prolinol (37% ee) or (-)-2-amino-1-butanol (11% ee) (Scheme 5, Table 2). The moderate chemical yields of these transformations (500-70%) can be ascribed to side-reactions of the ketones under the strongly basic conditions.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19840670325