(-)-(9R,10S)-10-acetyl-9,10-dimethylbicyclo[6.4.0]dodec-1(8)-ene: Optical resolution, catalyst systems, derivatives and olfactory properties

摘要

By separation of the enantiomers of the woody-ambery odorant 10-acetyl-9,10-dimethylbicyclo[6.4.0]dodec-1(8)-ene (rac-12) via their diastereomeric (-)-camphanoates, the (-)-(9R,10S)-isomer (9R,10S)-12 was determined to be the most powerful enantiomer. With an odor threshold of 0.19 ng/L it is about one hundred times stronger than its antipode. Racemic 10-acetyl-9,10-dimethylbicyclo[6.4.0]dodec-1(8)-ene (rac-12) was synthesized by an unusual [4+2]-cycloaddition of 4-methylenespiro[2.7]decane (10) and 3-methylbut-3-en-2-one (11) in the presence of Wilkinson's catalyst. However, attempts to induce optical activity with chiral rhodium(I) catalysts proved futile. Platinum(II)-DIOP catalysts furnished traces (0.05% GC yield) of (-)-(9R,10S)-10-acetyl-9,10-dimethylbicyclo[6.4.0]dodec-1(8)-ene [(9R,10S)-12] with an enantiomeric excess of around 40% ee. For further studies on the structure-odor correlation of woody odorants, two new tricyclic analogs of rac-12, (+/-)-(2R*,3S*,7S*)-2-methyltricyclo[7.6.0.0(3,7)]pentadec-1-(9)-en-4-one (18) and (+/-)-(2R*,3S*,7S*)-2,3-dimetbyltricyclo[7.6.0.0(3,7)]pentadec-1(9)-en-4-o ne (20) were synthesized and characterized. [References: 34]