Takashi Koike

Trifluoromethyl (CF3) and difluoromethyl (CF2H) groups are versatile structural motifs, especially in the fields of pharmaceuticals and agrochemicals. Thus, the development of new protocols for tri- and difluoromethylation of various skeletons has become a vital subject to be studied in the field of synthetic organic chemistry. For the past decades, a variety of fluoromethylating reagents have been developed. In particular, bench-stable and easy-to-use electrophilic fluoromethylating reagents su

Here comes the sun: A facile vicinal difunctionalization of alkenes, oxytrifluoromethylation, was established by visible-light-driven photoredox catalysis. Judicious choice of the CF3 source is key. Nucleophiles such as water, alcohols, and carboxylic acids can be used in this highly efficient (2–4 h) and regioselective (100 %) transformation using light-emitting diode (LED) lamps and natural sunlight. SET=single-electron transfer.

New and easy protocols for radical reactions have been developed.

Abstract A new strategy for the generation of carbon‐centered radicals via oxidation of alkyl‐, allyl‐, benzyl‐ and arylborates by visible‐light‐driven single electron transfer (SET) photoredox catalysis has been established. The generated radicals smoothly react with TEMPO and electron‐deficient alkenes to afford CO and CC coupling products, respectively. In this radical initiating system, cyclic organo(triol)borates turn out to be useful radical precursors.

A facile synthesis of trifluoromethylated alkenes by the radical-mediated trifluoromethylation of vinyltrifluoroborates has been developed. Togni's reagent serves as a CF(3) radical precursor in the presence of the photoredox catalyst [Ru(bpy)(3)](PF(6))(2) under visible light irradiation. This new photocatalytic protocol can be applicable to a wide variety of vinylborates containing electronically diverse substituents and hetero-aromatics.

We have developed a novel and simple protocol for the direct incorporation of a difluoromethyl (CF2 H) group into alkenes by visible-light-driven photoredox catalysis. The use of fac-[Ir(ppy)3] (ppy=2-pyridylphenyl) photocatalyst and shelf-stable Hu's reagent, N-tosyl-S-difluoromethyl-S-phenylsulfoximine, as a CF2 H source is the key to success. The well-designed photoredox system achieves synthesis of not only β-CF2 H-substituted alcohols but also ethers and an ester from alkenes through solvol

A regio- and stereoselective synthesis of trifluoromethylated alkenes bearing four different substituents has been developed. Stereocontrolled sulfonyloxytrifluoromethylation of unsymmetric internal alkynes with an electrophilic CF3 reagent, namely the triflate salt of the Yagupol'skii-Umemoto reagent, in the presence of an Ir photoredox catalyst under visible-light irradiation afforded trifluoromethylalkenyl triflates with well-predictable stereochemistry resulting from anti addition of the tri

Sonnige Aussichten: Photoredoxkatalyse mit sichtbarem Licht ermöglicht die einfache vicinale Difunktionalisierung von Alkenen durch Oxytrifluormethylierung. Entscheidend dabei ist die sorgfältige Wahl der CF3-Quelle. Nucleophile wie Wasser, Alkohole und Carbonsäuren können in dieser hoch effizienten (2–4 h) und regioselektiven (100 %) Umwandlung unter Einwirkung von LED- oder natürlichem Sonnenlicht eingesetzt werden. SET=Einelektronentransfer.

Abstract Tris(bipyridyl)ruthenium(II) ([Ru(bpy)3]2+: TB(II)) catalyzes oxidative coupling of enamines and aldehydes with 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) under irradiation of visible light to afford α-oxyaminated carbonyl compounds. The visible light irradiation is essential to generate the triplet excited state of ∗TB(II) which acts as an oxidizing agent. This is a new procedure for radical coupling based on single electron transfer mediated by photoactivated TB.

[reaction: see text] A well-defined chiral Ru catalyst RuCl(N-(p-toluenesulfonyl)-1, 2-diphenylethylenediamine)(eta(6)-arene) effectively promotes asymmetric transfer hydrogenation of 1-aryl-1,2-propanedione with HCOOH/N(C(2)H(5))(3), leading preferentially to optically active 1-aryl-2-hydroxy-1-propanone with up to 99% ee and 89% yield at 10 degrees C. The reaction at 40 degrees C gives anti-1-aryl-1, 2-propanediol with up to 95% ee and 78% yield. This is a highly efficient procedure for the sy

A simple and regiospecific aminohydroxylation of olefins by photoredox catalysis has been developed. N-protected 1-aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac-[Ir(ppy)3] and [Ir(ppy)2 (dtbbpy)](PF6) (ppy=2-pyridylphenyl, dtbbpy=4,4'-di-tert-butyl-2,2'-bipyridine). The present photocatalytic system allows for synthesis of vicinal aminoalcohol derivatives from olefins with various functional groups under mild reaction c

Recently, photoinduced radical difluoromethylation has emerged as a step-economical synthetic method of CHF2-containing compounds. In this article, difluoromethylation of alkenes, isonitriles and aryl bromides promoted by photoredox catalysis is described together with a non-catalytic photoinduced system. Representative reactions will be discussed for each highlighted difluoromethylating reagent. In addition, related monofluoromethylation with their corresponding monofluoromethylating reagents i

Abstract A photocatalytic hydroaminomethylation of olefins with N ‐protected aminomethyltrifluoroborates has been developed. This methodology provides a new strategy for the introduction of a primary aminomethyl group onto electron‐deficient CC bonds. This reaction constitutes a facile entry into synthetically useful γ‐aminobutyric acid (GABA) derivatives such as baclofen. magnified image