| Abstract
| - Both the organoplatinum and palladium complexes containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary have been used to promote the asymmetric [4 + 2] Diels−Alder reaction between diphenylvinylphosphine and 2-diphenylphosphinofuran. Of the chiral template, the platinum complex was found to be superior.
- The organoplatinum complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used efficiently to promote the asymmetric [4+ 2] Diels−Alder reaction between diphenylvinylphosphine and 2-diphenylphosphinofuranto generate the chelating diphosphine exo-cycloadduct, 4(R),5(R)-bis(diphenylphosphino)-7-oxabicyclo[2.2.1]hept-2-ene in 70% isolated yield. At room temperature, the reaction wascomplete in 5 d. However, the cycloaddition reaction proceeded at a significantly slower rateand exhibited a markedly lower stereoselectivity when the chiral platinum template wasreplaced by its organopalladium counterpart. The diphosphino-substituted oxanorbornenemetal complexes are stable and the oxygen−carbon bonds are inert toward treatments withstrong acids. Upon liberation from the metal ions, however, the chiral cycloadduct becomesunstable and undergoes the retro Diels−Alder reaction slowly to regenerate diphenylvinylphosphine and 2-diphenylphosphinofuran.
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