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Camphor-derived alcohols as chiral auxiliaries for asymmetric Pauson-Khand bicyclizations. Enantioselective synthesis of α-methoxyenones

1992; Elsevier BV; Volume: 433; Issue: 3 Linguagem: Inglês

10.1016/0022-328x(92)80156-r

1872-8561

Xavier Verdaguer, Albert Moyano, Miquel À. Pericàs, Antoni Riéra, Andrew E. Greene, J.F. Piniella, Ángel Álvarez-Larena,

Asymmetric Synthesis and Catalysis

The intramolecular Pauson-Khand reaction of enol and ynol ethers of Oppolzer's camphor-derived neopentyloxy alcohols is described. Bicyclic products are obtained in yields of up to 65% and with diastereoselectivities as high as 94:6 under very mild reaction conditions. The absolute configurations of the major stereoisomers obtained when (1R, 2S, 3R, 4S)-3-neopentyloxy-1,7,7-trimethylbicyclo- [2.2.1]heptan-2-ol is used as a chiral auxiliary are rationalized on the basis of the theoretically predicted preferential conformations of model precursors. A simple procedure for obtaining auxiliary-free, enantiopure bicyclic α-methoxyenones is also presented.