A highly reactive and robust chiral Brønsted acid catalyst, chiral N-triflyl thiophosphoramide, was developed. The first metal-free Brønsted acid catalyzed enantioselective protonation reaction of silyl enol ethers was demonstrated using this chiral Brønsted acid catalyst. The catalyst loading could be reduced to 0.05 mol % without any deleterious effect on the enantioselectivity.

A chiral Brønsted acid has been developed from cationic gold(I) disphosphine complex in the presence of alcoholic solvent and applied to enantioselective protonation reaction of silyl enol ethers of ketones. Various optically active cyclic ketones were obtained in excellent yields and high enantioselectivities including cyclic ketones bearing aliphatic substrates at the α-position. Furthermore, the application of this Brønsted acid was extended to the first Brønsted acid-catalyzed enantioselective protonation reaction of silyl enol ethers of acyclic substrates, regardless of their E/Z ratio.

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The first metal-free thermal protodeboronation of ortho- and para-phenol boronic acids in DMSO was developed. The protodeboronation was successfully applied to the synthesis of ortho- and meta-functionalized phenols using the boronic acid moiety as a blocking group and a directing group, respectively. Mechanistic studies suggested that this protodeboronation proceeds through the coordination of water to the boron atom followed by σ-bond metathesis.

We report a new hole transporting material (HTM) based on [2,2]paracyclophane triarylamine. Due to its higher charge mobility compared with spiro-OMeTAD, the solar cell device incorporating the new HTM achieved a high photovoltaic performance with a PCE of 17.6%.

Brønsted acid catalysis has emerged as a new class of catalysis in modern organic synthesis. However, in order to make the utility of the Brønsted acid catalysis as broad as the well-developed Lewis acid catalysis, it is desirable to develop Brønsted acids demonstrating both high reactivities and selectivities. In this feature article, we will present our achievement in the design and development of strong Brønsted acids and their application to organic reactions. Furthermore, we will describe the Tf(2)NH-catalyzed Mukaiyama aldol reaction of super silyl enol ethers. We also will highlight the differences in reactivity and chemo- and stereo-selectivity between Brønsted and Lewis acid catalysis.

The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to Brønsted acid itself depending on the reaction temperature.The addition of silyl enol ethers to carbonyl compounds, known as the Mukaiyama aldol reaction, has been the subject of extensive investigation due to the usefulness of products containing one new carbon-carbon bond and up to two new stereogenic centers. 1, 2 Although many successful examples employing either Lewis acid 3 or Lewis base 4 catalysts have been developed for enantioselective Mukaiyama aldol reactions, only a few examples of chiral Brønsted acids catalyzed enantioselective Mukaiyama aldol reactions have been reported. Rawal reported a TADDOL catalyzed Mukaiyama aldol reaction of aldehydes and acylphosphonates with silyl enol ethers of amides. 5 Jørgensen described a chiral bissulfonamide Brønsted acid catalyst in a Mukaiyama aldol reaction with silyl ketene acetal. 6 However, these Brønsted acid catalyzed asymmetric Mukaiyama aldol reactions generally required highly activated substrates for both nucleophiles and electrophiles presumably due to their lower acidities.Most recently List and coworkers have developed a disulfonimide derived from BINOL as a new chiral Brønsted acid catalyst and applied it to an asymmetric Mukaiyama aldol reaction. 7 Although this new catalyst showed potential to solve the previous problems of the asymmetric Mukaiyama aldol reaction with weak Brønsted acids, such as limited substrate scope, this catalyst system still needs to use reactive silyl ketene acetals as nucleophiles. In addition, the active catalyst in this system was shown to be the silylated Brønsted acid acting as Lewis acid rather than Brønsed acid itself. To the best of our knowledge, there have been no reports of Brønsted acid catalyzed enantioselective Mukaiyama aldol reaction using less reactive silyl enol ethers of ketones as nucleophiles. 8 Moreover, mechanistic studies revealed that the actual catalyst in this system is the Brønsted acid itself rather than the silylated Brønsted acid.Since Akiyama and Terada's seminal reports in 2004, 9,10 chiral phosphoric acid catalysis to activate π-electrophiles towards nucleophilic attacks has been one of the growing fields in asymmetric catalysis. 11 Many enantioselective addition reactions to imines have been achieved with these chiral Brønsted acids, 12 however, successful application of these acids to reactions through carbonyl group activation has remained challenging due to their lower reactivities. 13 In order to increase the reactivities of chiral phosphoric acid catalysts and thus broaden their applicabilities, we have recently developed chiral N-triflyl oxo-, thio, and selenophosphoramides ...

A new protocol for the synthesis of 2,2'-bisindole-3-acetic acid derivatives from aldimines derived from 2-aminocinnamic acid derivatives and indole-2-carboxaldehyde was developed via a cyanide-catalyzed imino-Stetter reaction. With this protocol, the divergent total syntheses of arcyriaflavin A, a representative indolocarbazole natural product, and calothrixin B, a representative indolo[3,2-j]phenanthridine natural product, were completed using a 2,2'-bisindole-3-acetic acid derivative as the common intermediate.