ISSN:
0009-2940
Keywords:
Carbanions
;
Protonation, diastereoselective
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The diastereoselectivity of the kinetically controlled protonation of carbanions derived from 4-tert1-butyl-1-X-cyclohexanes (1: X=CN, 2: X=CO2Me, 2-Si: X=C(OMe)OSiMe3, 3: X=COPh, 4: X=SO2Ph) is systematically investigated. By variation of (a) the base for deprotonation of 1 - 4, (b) OH-, NH-, and CH-proton sources, (c) added salts, Lewis bases, and acids, (d) solvents (cf. Tables 2 - 5) the cis/trans ratios of diastereomers could be influenced as follows: 1: 41/59→85/15; 2: 26/74→73/27; 3: 26/74→〉93/〈3; 4: 1/99→37/63. The results are discussed with regard to structure and aggregation of 1Li to 4Li and compared with relevant data from the literature. It is concluded that so far an empirical approach to high diastereoselectivities cannot be avoided and that the results cannot be predicted from the ratios obtained by the much slower alkylation reactions.
Additional Material:
8 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260522
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