Development of environmentally benign and highly active acid-base catalysts and their synthetic application

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The design of small but highly functional artificial catalysts is very important for practical organic synthesis. We have succeeded in the rational design of small and simple catalysts and related reactions based on acid-base combination chemistry. Acid-base combined catalysts can be classified into three types: (1) acid-base combined salt catalysts (Type A), (2) conjugate acid-base catalysts (Type B), and (3) non-conjugate acid-base catalysts (Type C):1. Acid-base combined salt catalysts (Type A)1-1. Bronsted acid-base combined salt catalysts (Type A-1): bulky diarylammonium pentafluorobenzenesulfonates as mild and extremely active dehydrative ester condensation catalysts; chiral ammonium alkanesulfonates as asymmetric Diels-Alder catalysts1-2. Lewis acid-base combined salt catalysts and reagents (Type A-2): magnesium ate complexes derived from Grignard reagents and alkyllithium as highly alkyl-selective reagents to ketones; zinc ate complexes as catalysts for the highly alkyl-selecti … More ve addition of Grignard reagents to ketones and aldimines1-3. Cation-anion pair catalysts (Type A-3): lithium N, N-diisopropylamide in Haller-Bauer and Cannizzaro reactions; chiral lithium binaphtholate aqua complex as a highly effective asymmetric catalyst for trimethylsilylcyanation1-4. Cation-a complex catalysts (Type A-4): chiral Cu(II)・L-DOPA-derived monopeptide complex as an asymmetric Diels-Alder and Mukaiyama-Michael catalyst2. Lewis acid-base conjugate catalysts (Type B): molybdenum oxides as highly effective dehydrative cyclization catalysts directed toward the synthesis of oxazolines and thiazolines (Type B-1(monoconjugation)); zinc(II)・3,3'-diphosphinoyl-BINOLates in the asymmetric addition of organozinc reagents to aldehydes (Type B-2 (triconjugation))3. Bronsted acid-Lewis base non-conjugate asymmetric catalysts (separated type) (Type C): L-histidine-derived sulfonamide as a minimal artificial acylase for the kinetic resolution of racemic alcoholsThus, we developed new acid-base combined catalysts bearing excellent functions such as dual activation, control of nucleophilicity and basicity, asymmetric induction, hydrophobic effect, and so on. Current research is focused on the development of artificial highly functional catalysts which are superior to natural enzymes. Less