| New Lewis Acid-Assisted Chiral Bronsted acid (chiral LBA), chiral 1,2-diaryl-1,2-ethanediol and tin tetrachloride, was developed for highly enantiolesective protonation of silyl enol ethers. The most significant finding is that I was able to specify the conformational direction of the O-H bond of LBA, which has some asymmetric inductivity, by X-ray diffraction analysis.;In addition to that, I studied chiral LBAs prepared from titanium tetrachloride and chiral 2-methoxy-2-alkylethanol. Although enantioselectivity was still not high enough, they showed high reactivity. Thus, I confirmed the importance of the preparation conditions of chiral LBA for the enantioselectivity.;Highly reactive and acidic chiral Bronsted acid catalyst, chiral N-triflyl phosphoramide, was developed for highly enantioselective Diels-Alder reaction of alpha,beta-unsaturated ketone with silyloxydienes. Also, I designed chiral super Bronsted carbon acid.;I described the reversal of chemoselectivity in Diels-Alder reaction and the utility of Bronsted acid as an effective catalyst for the Diels-Alder reaction of alpha,beta-unsaturated ketone. |
