ISSN:
0009-2940
Keywords:
Umpolung
;
α,β-Unsaturated aldehydes
;
Acyloins
;
Nucleophilic acylation
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Trimethylsilyl Cyanide - A Reagent for Umpolung, XVII. - Diastereoselectivity in Nucleophilic Acylations of α-Chiral Carbonyl Compounds with α,β-Unsaturated Aldehydes after UmpolungAnions 3A obtained from α,β-unsaturated aldehydes 2 after umpolung with trimethylsilyl cyanide (2a) add in ca. 45-75% yield to the α-chiral aldehydes and ketones 4. In THF, 2:1 products 5 are formed, whereas in ether 1:1 adducts 8 are obtained. Formation of 8 proceeds with high chiral 1,2-induction, if 4 carries α-phenyl groups (syn/anti-8 86:14 to 96:4) whereas with α-ethylgroups in 4 only minor stereoselection is observed (syn/anti-8 ca. 56:44).
Notes:
Die anionen 3A der mit Trimethylsilycyanid (2a) umgepolten α,β-ungesättigten Aldehyde 1 addieren sich mit ca. 45-75% Ausbeute an die chiralen Aldehyde und Ketone 4 in THF zu den 2:1-Addukten 5, in Ether zu den 1:1-Addukten 8. Hohe chirale 1,2-Induktion bei der Bildung von 8 wird durch α-Phenylgruppen in 4 bewirkt (syn/anti-8 86:14 bis 96:4), während α-Ethylgruppen in 4 nur geringe Stereoselektion bewirken (syn/anti-8 ≍ 56:44).
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19891221114
