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- Title
Reversed Stereochemical Course of the Michael Addition of Cyclohexanone to β-Nitrostyrenes by Using 1-(Trimethylsiloxy)cyclohexene/Dichloro(diisopropoxy)titanium. Preliminary Communication.
- Authors
Seebach, Dieter; Brook, Michael A.
- Abstract
Induced by a stoichiometric excess of dichloro(diisopropoxy)titanium, 1-(trimethylsiloxy)cyclohexene and p-substituted β-nitrostyrenes (Y = H,CH3,CH3O,CN) combine in CH2Cl2 solution at −90° preferentially with relative topicity ul - opposite to the corresponding reaction of enolates or enamines. The primary products are the bicyclic nitronates 3-5 which can be separated, and which are cleaved by KF in MeOH to give the aryl(nitroethyl)-substituted cyclohexanones 1 and 2 ( Tables 1 and 2, two typical procedures are given). The major products (2:1 to 4:1) are the hitherto not readily available diastereoisomers 2 of l-configuration. Instead of being solvolyzed, the bicyclic nitronate 5 can be used for nitroaldol additions (→ 6) and for [3 + 2]-dipolar cycloadditions (→ 7), diastereoselectively furnishing products with 4 asymmetric C-atoms (not counting acetal centers). The Michael addition described here is yet another example of an ul-combination of trigonal centers induced by Lewis acids, overriding the influence of the configuration of the donor component.
- Publication
Helvetica Chimica Acta, 1985, Vol 68, Issue 2, p319
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19850680205