Multiply arylated (hetero) arenes are intriguing structural motifs in functional molecules, such as natural products, pharmaceuticals and functional organic materials. In recent decades, many synthesis methods of multiply arylated (hetero)arenes have been reported. As a subclass of multiply arylated arenes, fully arylated (hetero)arenes have also flourished as a unique structural class in functional organic materials and biologically active compounds. Despite the successful application of fully arylated (hetero)arenes with different aryl substituents, the synthesis of such (hetero)arenes has not been explored compared to partially arylated arenes due to the difficulty of synthesizing sterically hindered and highly unsymmetrical aromatic cores. This review reports the synthesis of fully arylated (hetero)arenes bearing more than two different aryl substituents and categorizes this emerging topic by the type of (hetero)arene core, focusing on the methods employing cross-coupling reaction including direct C-H arylation.
Enormous attention has been paid to the fluorine-containing organic molecules in the field of medicinal, pharmaceutical, and material chemistry since fluorine or fluoroalkyl substituents incorporated into organic molecules often affect their chemical as well as physical properties. Therefore, significant effort has been devoted to the development of effective synthetic methods for organofluorine compounds. Recently, we have developed a regioselective synthetic method for perfluoroalkyl-substituted condensed polycyclic aromatic compounds, e.g. anthracenes, pentacenes, and pentaphenes. This article describes the effective introduction of perfluoroalkyl substituents into the condensed polycyclic aromatic compounds in a regioselective manner. In addition, evaluation of physical properties of the fluorine-containing pentacenes is described as well.
Aniline-type and DMAP-type biaryl amino acids, as well as their surrogates were developed as organocatalysts with molecular recognition properties.
Aniline-type catalyst made regio- and stereoselective intramolecular cross-aldol reaction of unsymmetric aliphatic dial possible by fine discrimination of formyl groups. The key for discrimination of formyl groups is mild reactivity of aniline-type catalyst.
A series of biaryl-type DMAP catalysts having an internal carboxylate ion were also developed for investigating the proper location of the carboxylate ion that effectively accelerates the DMAP catalyzed acylation (carboxylate effect). By evaluating catalytic activities of these DMAP derivatives, the carboxylate group located in close proximity to the pyridine ring in a face-to-face geometry was determined to be an effective general base to accelerate the acylation.
Preparation of aniline-type binaphthyl amino acid via Pd catalyzed domino-coupling reaction of o-bromoaryl amides is also described in this account.
Chiral α-hydroxycarboxylic acids and their derivatives bearing a tetrasubstituted α-carbon atom are well-recognized chiral synthons and components of various pharmaceuticals and biologically active natural products. Despite their high demand, preparative methods of these compounds are quite limited due to the difficulty in achieving stereoselective construction of the tetrasubstituted carbon stereogenic center at the α-position. To address this issue, we developed asymmetric nucleophilic addition reactions of 5H-oxazol-4-ones to carbon electrophiles using chiral bicyclic guanidine catalysts containing a hydroxyl group at the appropriate position as a preparative method of α-tetrasubstituted hydroxycarboxylic acid derivatives. In this article, we introduce the nucleophilic addition reactions with several types of electrophiles, such as aldehydes, alkynyl carbonyl compounds, allenyl carbonyl compounds, vinyl ketones, dienones, and 2-chloroacrylnitrile. Derivatizations of the products of these reactions into corresponding α-hydroxycarboxylic acid derivatives and their application to a natural product synthesis are also described.
The [1,2]-phospha-Brook rearrangement involves the migration of the phosphorus moiety of the alkoxide of an α-hydroxyphosphonate from carbon to oxygen to generate an α-oxygenated carbanion. We have been focusing on the [1,2]-phospha-Brook rearrangement as a useful tool for the development of novel synthetic reactions under Brønsted base catalysis. For instance, we utilized the rearrangement for the catalytic generation of carbanions of less acidic compounds through the formal umpolung process from the corresponding carbonyl compounds. We have developed catalytic addition reactions of carbanions, such as enolates derived from less acidic amides and esters, α-oxygenated allyl anions that can serve as homoenolate equivalents and benzyl anions, as nucleophiles. We have also developed new efficient syntheses of functionalized allenes involving the generation of propargyl anions followed by regioselective protonation. The allenes were further applied to cycloisomerization to afford heterocyclic compounds, such as 2-aminofuran derivatives and indolizine derivatives. On the other hand, we utilized the [1,2]-phospha-Brook rearrangement for facilitating catalyst turnover in Brønsted base-mediated processes. Specifically, the [2,3]-Wittig rearrangement and the α-oxygenation of carbonyl compounds, which generally require a stoichiometric amount of Brønsted bases, have been successfully combined with the [1,2]-phospha-Brook rearrangement to proceed in a catalytic fashion.
Benzo[b]phosphole oxides exhibit attractive optical and electronic properties for applications as materials for organic light-emitting devices, photovoltaics and field-effect transistors. Recently, benzo[b]phosphole oxides introduced an electron-donating substituent have been emerged. These molecules show strong fluorescence and solvatochromism depending on the electron-donating substituent. This review highlights recent progress in developing donor-acceptor-type benzo[b]phosphole oxides and their photophysical properties.