Hisashi Yamamoto

Chemists' ability to perform syntheses on a routine basis is due in large part to the development of new methods for synthesizing organic molecules which would have been impossible just a few decades ago. The availability of such new methods of sythesis has increased not only the range of structures which can be assembled but also the ease and economy of synthesis. During the past 30 years of his research, Professor Hisashi Yamamoto has had a tremendous impact on the field of organic chemistry through his reports of dramatic new advances in organic synthesis. Yamamoto's publications are numerous (over 450), and almost every one of them has provided an innovative new development or idea. Applications of this original and versatile chemistry have allowed him and other scientists to realize truly efficient syntheses of organic molecules of both theoretical and practical importance.

Hisashi Yamamoto has uncovered novel aspects of Lewis and Brønsted acid catalysts in selective organic synthesis. During his career he has discovered a wide variety of powerful new synthetic reactions, reagents, and catalysts based on acid catalysis chemistry. Through his dedicated efforts, Lewis and Brønsted acid are now recognized as major tools in the synthesis of both simple and complex organic molecules. Among Yamamoto's many superb contributions the following are especially worthy of mention.

His research in the area of organoaluminum chemistry has had a great impact on synthetic organic chemistry. The strong Lewis acidity of organoaluminum compounds appears to account for their strong tendency to form a stable 1:1 complex. Thus, the coordination of molecules invariably causes a change of reactivity, and the coordinated group may be activated or deactivated depending upon the type of reaction. Furthermore, with coordination of organic molecules an auxiliary bond can become coupled to the reagent and promote the desired reaction. In short, the reagents make a combined Lewis acid - Lewis base attack on a substrate with less activation energy, a field opened by Yamamoto's early and highly original studies. His aluminum amide reagents for epoxide rearrangement, biogenetic-type terpene synthesis, and the Beckmann rearrangement-alkylation reaction sequence are notable examples.

More recently, he has developed new asymmetric oxidation processes based on an acid catalysis concept. His nitroso chemistry offers an entirely new access to selective organic synthesis and provides catalytic enantioselective reaction to introduce oxygen and/or nitrogen into the molecule. His pyridine based nitroso- and azo-hetero-Diels-Alder provides powerful tool for asymmetric synthesis. He also recently reported asymmetric epoxidation of homoallylic alcohols based on new vanadium catalyst, one of the most difficult asymmetric oxidations to date.

After moving to Chicago, he proposed the use of 8-hydroxyquinole based chiral Lewis acid catalysis. The catalyst is designed as a rigid metal complex of cis-b-configuation. The reagent turned out to be a brand-new "privileged ligand" for asymmetric synthesis. Catalytic asymmetric pinacol coupling, NH reaction, Mukaiyama-Michael addition, and Pudovik reactions are now able to proceed with complete enantioselectivities.

His laboratory is also noted for its introduction of metal reagents that allow highly selective SN2 cross coupling with carbonyl and allylic electrophiles. Allylic organobarium reagent, so-called "Yamamoto's reagent", reacts with a variety of electrophiles selectively at less substituted termini with complete stereospecificity, resolving a long-standing problem in terpene synthesis.