p-Hydroxybenzylierung von Carbanionen mit Chinonmethid-liefernden Verbindungen

p-Hydroxybenzylation of Carbanions with Quinonemethide Precursors. 3,5-Dialkylated 4-hydroxy-benzyl derivatives 4, 5 and 6 are useful starting materials for the p-hydroxybenzlation of carbanions derived from activated methylene compounds 7 . The reaction presumably proceeds through intermediate formation of quinonemethides 2 . The scope of the reaction is discussed.     

Enantioselektive 1,4-Additionen von metallorganischen Verbindungen an konjugierte Systeme im chiralen Medium DDB

Enantioselective 1,4-additions of organometallic compounds to conjugated systems in the chiral medium DDB

1 DDB = 1,4-Dimethylamino-2,3-dimethoxybutan (= 2,3-Dimethoxy-N,N,N′,N′-tetramethyl-1,4-butandiamin).

The chiral methoxyamine DDB is used as a cosolvent to add achiral Li-, Cu-, and Zn-organic compounds enantioselectively to prochiral β-carbon atoms of α, β-unsaturated aldehydes, ketones, nitro compounds and ketene-thioacetals (Tables 1 and 2). The selectivity generally ranges from 55:45 to 63:27, in one case ( 9b ) an enantiomeric excess of 43% was obtained.     

Enantioselektive Cyclopropanierung von 1,1-Diphenylethylen und Diazoessigester mit Kupfer-Katalysatoren

Copper(II) compounds catalyze the reaction of 1,1-diphenylethylene with diazoacetic acid ethylester. The main product is 2,2-diphenylcyclopropane carboxylic acid ethylester. The formation of the carbene dimerization products fumaric and maleic acid diethylester can be suppressed by the continuous addition of diazoacetic acid ester to 1,1-diphenylethylene.37 optically active ligands, partly new, were combined with copper(II)-acetate to givein-situ-catalysts. In five cases isolated copper complexes were used as catalysts. The best optical inductions in the formation of 2,2-diphenylcyclopro-pane carboxylic acid ethylester with up to 65.6% ee were achieved withSchiff base ligands, which derive from salicylaldehyde and amino alcohols, obtained from amino acid esters and phenylGrignard.

Prof. Dr.Karl Schlögl, Universität Wien, mit den besten Wünschen zum 60. Geburtstag gewidmet.