Studies on Remote Asymmetric Induction Using Chiral Pyrrolyl Sulfoxides and its Catalytic Reactions

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1. Diels-Alder reaction of 2-(p-tolylsulfinyl) pyrrolyl enones {(E)-cinnamoyl, (E)-pent-2-enoyl and crotonoyl} with cyclopentadiene proceeded smoothly to give the corresponding endo adducts as a single isomer (>90% diastereoisomeric excesses) in the presence of a Lewis acid such a lanthanoid triflate and aluminum (III) chloride.2. Conjugate addition reaction to chiral 2-(p-tolylsulfinyl) pyrrolyl (E)-cinnamoyl and crotonoyl ketones using (di) alkyl cuprates afforded the corresponding two addition products with up to 30% diastereoisomeric excesses. On the other hand, addition reactions to chiral 2-(p-tolylsulfinyl) pyrrolyl (E)-cinnamoyl ketones with (di) aryl cuprates such as o-tolyl-, p-tolyl-, and (1-naphthyl)-cuprates afforded the corresponding addition products which have R configuration with >90% diastereoisomeric excesses. Similar reactions to the crotonoyl derivative by arylcuprates afforded the addition products with modest to excellent diastereoselectivities.The absolute stereochemistry at newly formed asymmetric carbon center of the major products was determined by X-ray analysis or by transformation into the known compounds by alcoholysis. In particular for these two addition reactions, the auxiliary (i.e.the sulfinyl pyrrole) was recovered by alcoholysis of the products without any loss of optical purity.