ORGN 1 |
Studies in asymmetric nucleophilic addition to arene chromium tricarbonyl complexes
| Anthony J. Pearson and Harinandini Paramahamsan. Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 |
Dearomatisation of arenes by nucleophilic addition to the corresponding arene chromium tricarbonyl complexes leads to useful substituted cyclohexadienes and cyclohexenones. Studies in chiral auxiliary directed addition of the enolate of tert-butyl acetate have led to remarkable 1,5 asymmetric induction with diastereoselectivities as high as 33:1. Excellent selectivities were obtained when using camphor derived aryl isoborneols as chiral auxiliaries and trimethylsilyl group in the para position. Interesting reversal in selevtivity was observed in a few cases. Multiple stereoelectronic factors seem to influence the selectivity of nucleophilic addition. Nucleophilic addition of tert-butyl propionate lead to the introduction of vicinal sterocenters. Vicinal stereocontrol is possible by suitable selection of chiral auxiliary, para substituent and nucleophile. |
| |
|
|