Reactionsof five-and/or six-membered-ring ketonesl-5 possessing an o-halogenoalkyl group and a',p'unsaturated ester function at the m-position with diorganocuprates afforded the oxapropellane compounds 20-24 in a one-pot, three-step procedure via 1,4-addition followed by intramolecular aldol con densat ion a nd 0a I ky lat ion. S i m i la r react i on of a,a' -d isu bst it u ted cyc lope nta none 6 afforded bicyclic products 28 and 29.Conjugate addition of diorganocuprates is one of the valuable tools of organic synthesis. Some applications of conjugate addition for ring construction have been reported, and which may be classified into two groups. One is the double cyclization by intramolecular conjugated addition of a carbanion generated by base, and C-trapping of the resulting enolate with an intramolecular electrophile [eqn. ( l)]. As examples of this type of reaction, there are the double-Michael reaction,' 1,4addition-aldol condensation,2 and 1,4-addition-s~bstitution.~ In these cases, bicyclic compounds are obtained from acyclic substrates. The other group consists of monocyclizations by Ctrapping of the enolate generated by the conjugated addition of a diorganocuprate [eqn. (2)]. As examples of this type, there are 1,4-addition-a1dol condensation and 1,4-additionsubstitution with halide and e p ~x i d e . ~In these cases, monocyclic compounds are obtained from acyclic substrates. The ynenone system is also applicable to this type of r e a ~t i o n . ~ These reactions have been found to be effective for stereoselective construction of cyclic compounds, especially polycyclic compounds.R2CuLi \ Full details of the X-ray structure analysis of compound 6 are given in C. Fang, K. Suganuma, H. Suemune, N. Marubayashi and K. Sakai, Chem. Pharm. Bull. manuscript in preparation.

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