π-Acidic metal-catalyzed cyclization reaction is one of the most efficient methods to construct highly elaborate molecular skeletons in a single operation under mild reaction conditions. These transformations often involve cleavage of σ bonds. Investigations into catalytic skeletal rearrangement have mainly utilized alkynylamines, alkynylalcohols, enynes, and propargylic esters as substrates. In this article, I report our recent findings on π-acidic metal-catalyzed reactions via cleavage of σ bonds between major elements in body, such as carbon, nitrogen, oxygen, and sulfur, producing multisubstituted heterocycles in an atom-efficient manner. That is, (a) catalytic carbon-heteroatom bond addition of ortho-alkynylphenyl ethers, -anilines, and -phenyl sulfides and (b) catalytic skeletal rearrangement of O-propargylic oximes.
Although “central chirality” based on stereogenic carbon atoms is arguably the most common chiral element in organic chemistry, chiral molecules devoid of stereogenic centers play important roles in stereoselective organic transformations. Among these chiral compounds with “non-centrochirality”, planar-chiral transition-metal complexes have been utilized as chiral ligands, chiral catalysts, or chiral building blocks in asymmetric synthesis. However, enantiomerically enriched forms of these compounds are primarily obtained by rather classical methods. Examples of catalytic enantioselective induction of planar-chirality in transition-metal species have been extremely rare and still a developing area in this field. In this review article, catalytic asymmetric synthesis of various “planar-chiral transition-metal complexes” are surveyed in a comprehensive manner.
Electron-transfer behaviors of conjugated polymers on electrode (electrochemical doping) have been studied well for the purpose of electrochemical device applications such as conducting material and electrochromic material. In this study, we treated a charged (doped) state of conjugated polymers as an intermediate for following chemical reactions based on the concept of electroorganic synthesis. The post-functionalization of conjugated polymers was successfully achieved when a reactive dopant (conter ion derived from electrolyte) was used for the electrochemical reactions. For example, the polymer reactions such as anodic halogenations, cathodic reduction, and gradient oxidation reaction on bipolar electrode were successfully carried out to tune the optical and electrochemical properties of the polymers.
Pietra and co-workers reported isolation of (−)-agelastatins A and B from the deep water marine sponge Agelas dendromorpha collected in the Coral Sea near New Caledonia. The structure of these alkaloids featuring the architecturally unique tetracyclic array, coupled with their significant biological activity and scarce availability from marine organisms, has stimulated the synthetic community, resulting in inventive syntheses from eleven different research groups. In this review, these synthetic studies of agelastatin A showcasing elegant and powerful modern synthetic methodologies, are summarized.
Phosphole has a low aromaticity and exhibits characteristic optical and electrochemical properties derived from the phosphorus-bridged 1,3-diene π system. In addition, phosphole has an active lone pair at phosphorus. The most remarkable feature of the phosphole-based π-systems is that their fundamental properties are tunable by chemical functionalizations at the phosphorus center. In this regard, phosphole-based π-systems are now regarded as one of the future materials for use in optoelectronics. In this article, we would like to briefly summarize our recent results on the synthesis of novel π-conjugated phosphole derivatives with representative examples, which contain phosphole-vinylene, phosphole-acetylene, phosphole-heterole, phosphole-benzene, phosphole-phosphole, benzo[c]phosphole, acenaphtho[c]phoshole, and diacenaphtho[b,d]phosphole skeletons. The target compounds were successfully prepared by two main approaches, titanacycle method and Stille coupling. Selected structural, optical, and electrochemical data for a few derivatives are also presented. The results described herein would give valuable information and guidelines for designing phosphole-based opto-electrochemical materials.
This article describes the chirality sensing systems based on changes in conformation of dynamic terephthalamide hosts from a nonhelical form to a helical form with biasing to prefer one handedness upon complexation with a chiral guest through supramolecular transmission of chirality. The syn form is endowed with the ability to capture a ditopic guest through hydrogen bonds at the amide carbonyls; thus in a complexed state, a strong CD signal is produced thanks to a helical conformation induced by the conformational change and a biased handedness. Attachment of chirality to the terephthalamide host itself leads to an intrinsic preference in the sense of dynamic helicity in a helical syn form. Cooperative transmission of chiralities within the host and from the guest enables to further design an advanced sensing system with stereospecific chiroptical modulation, based on a stereospecific change in conformation of the chiral dynamic host upon complexation with a pair of enantiomeric guests.
Even in recent days, the SN2 reaction on vinylic carbons is not very common. This reaction pathway has been considered as an unlikely mechanism for a long time. However, recent investigations clearly indicate that nucleophilic attack on the σ* orbital of Csp2-LG bond is viable. In this short review, representative examples of this type of reaction are outlined.
Nanoporous materials are important in applications such as molecular separations, catalysts and gas storage. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and nanoporous polymers have dominated this research area. By contrast, discrete organic molecules tend to pack efficiently in solid state, leaving as little empty space as possible, which leads to non-porous materials. This review will highlight the recent developments with discrete organic cage molecules that are porous in solid state.
The story of the development for Pd mediated aerobic oxidation reactions in Stahl laboratory was described. The use of electron-deficient ligand has been found to achieve unprecedented levels of reactivity at lower temperature in aromatic C-H activation. This type of ligand enables us to demonstrate versatile and efficient strategy for the synthesis of substituted aromatic molecules via aerobic dehydrogenation of six-membered ring.