Hisashi Yamamoto

Bio: Hisashi Yamamoto is an academic researcher from Chubu University. The author has contributed to research in topics: Enantioselective synthesis & Catalysis. The author has an hindex of 79, co-authored 1476 publications receiving 22398 citations. Previous affiliations of Hisashi Yamamoto include King Abdulaziz University & University of Chicago.

Scandium Trifluoromethanesulfonate as an Extremely Active Lewis Acid Catalyst in Acylation of Alcohols with Acid Anhydrides and Mixed Anhydrides.

Abstract: Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic acids.

Design of acid-base catalysis for the asymmetric direct Aldol reaction.

Abstract: Proper design of acid-base catalysis has been shown to be effective for achieving high reactivity and selectivity in the asymmetric direct aldol reaction during the development of diamine-Bronsted acid types of catalyst. In this study, two principal approaches have been implemented to create a new type of catalysis and high catalytic efficiency: one is the creation of a highly viable acidic function within acid-base catalysts; the other is the creation of rather complicated but more cooperatively arranged hydrogen-bond networks that would be expected to stabilize a transition state, thereby promoting new reactivity and selectivity.

Direct Condensation of Carboxylic Acids with Alcohols Catalyzed by Hafnium(IV) Salts

Abstract: In order to promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excesses of either carboxylic acids or alcohols are normally needed. We show that the direct condensation of equimolar amounts of carboxylic acids and alcohols can be achieved with the use of hafnium(IV) salts, such as commercially available hafnium(IV) chloride and hafnium(IV) tert-butoxide. The present method can be applied to direct polyesterification and may be suitable for large-scale operations.

Organic Photoredox Catalysis

Abstract: In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Weak coordination as a powerful means for developing broadly useful C-H functionalization reactions.

Abstract: Reactions that convert carbon–hydrogen (C–H) bonds into carbon–carbon (C–C) or carbon–heteroatom (C–Y) bonds are attractive tools for organic chemists, potentially expediting the synthesis of target molecules through new disconnections in retrosynthetic analysis. Despite extensive inorganic and organometallic study of the insertion of homogeneous metal species into unactivated C–H bonds, practical applications of this technology in organic chemistry are still rare. Only in the past decade have metal-catalyzed C–H functionalization reactions become more widely utilized in organic synthesis.Research in the area of homogeneous transition metal–catalyzed C–H functionalization can be broadly grouped into two subfields. They reflect different approaches and goals and thus have different challenges and opportunities. One approach involves reactions of completely unfunctionalized aromatic and aliphatic hydrocarbons, which we refer to as “first functionalization”. Here the substrates are nonpolar and hydrophobic a...