Asymmetric Synthesis of Protected Cyclohexenylamines and Cyclohexenols by Rhodium‐Catalyzed [2+2+2] Cycloaddition

Abstract

It has been established that cationic rhodium(I)/ axially chiral biaryl bis(phosphine) complexes catalyzet he asymmetric [2+ +2+ +2] cycloaddition of 1,6-enynes with electron-rich functionalizeda lkenes,e namides,a nd vinyl carboxylates,t op roduce the corresponding protected cyclohexenylamines and cyclohexenols.I nterestingly,r egioselectivity depends on structures of substrates.The present cycloaddition was successfully applied to the enantioselective total synthesis of (À)-porosadienone by using the amide moiety as al eaving group.Scheme 5. Transformations of chiral bicyclic cyclohexenes 3 and 4. mCPBA = m-chloroperbenzoic acid.Scheme 6. Enantioselective total synthesis of (À)-porosadienone [(À)-10]. THF = tetrahydrofuran. Scheme 4. Plausible mechanisms for formation of 3-5.