143170-89-2Relevant academic research and scientific papers
3-Azabicyclic Ketones from 1,3-Dialkoxy-2-azapropenylium Salts and Enamines of Cyclic Ketones
Schleimer, Richard,Hornig, Knut,Moeller, Manfred H.,Wuerthwein, Ernst-Ulrich
, p. 133 - 142 (2007/10/02)
1,3-Diethoxy-2-azapropenylium salts 1 are powerful biselectrophiles and react diastereoselectively with enamines of five-membered ring ketones 2 to yield novel 3-azabicyclooct-2-en-8-ones 5 after hydrolysis of the intermediate iminium salts 3, 4.Some of the iminium salts 3 can be hydrolyzed further to provide the diketo imines 6.With enamines of six-membered ring ketones 7 the 3-azabicyclonon-2-en-9-ones 10, 11 are obtained after hydrolytic workup.Mixtures of diastereomers 10/11 are found in the case of 7a,b, whereas with 7g-j the endo-phenyl derivatives 10 are formed exclusively.With the unsymmetrical enamine 7b only one regioisomer is observed.The decalone enamine 12 reacts with 1a to yield the tricyclic iminium salt 13. - The configuration of the bicyclic products has been determined by using NMR spectroscopic techniques (COSY, polarisation transfer by long range couplings); an X-ray analysis of compound 10a is used as basis for the NMR assignments.General rules for the determination of the stereochemistry of these azabicyclic systems by 1H-NMR shift arguments are derived. Key Words: 2-Azapropenylium salts / Enamines / 3-Azabicyclooct-2-en-8-ones / 3-Azabicyclonon-2-en-9-ones / Stereochemistry
