Dynamic Kinetic Resolution of Hetero biaryl Ketones by Zinc- Catalyzed Asymmetr ic Hydrosil ylation

Adiastereo- and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile hetero- biaryl ketones is described. The DKR proceeds by zinc- catalyze dhydrosilylation of the carbonyl group ,thus leading to secondary alcohols bearing axial and central chirality .The strategy relies on the labilization of the stereogenic axis that takes place thanks to aLewis acid–base interaction between anitrogen atom in the heterocycle and the ketone carbonyl group .The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N-ligands or appealing axially chiral, bifunctional thiourea organocata- lysts.Ministerio de Ciencia e Innovación (Grants CTQ2016-76908-C2-1-P, CTQ2016-76908-C2-2-P, contract RYC-2013-12585)European FEDER FundsJunta de Andalucía (Grant 2012/FQM 10787)European Union - Marie Skłodowska-Curie (COFUND—Grant Agreement n 8 8 291780

A Dynamic Kinetic Asymmetric Heck Reaction for the Simultaneous Generation of Central and Axial Chirality

A highly diastereo- and enantioselective, scalable Pd-catalyzed dynamic kinetic asymmetric Heck reaction of heterobiaryl sulfonates with electron-rich olefins is described. The coupling of 2,3-dihydrofuran or N-boc protected 2,3-dihydropyrrole with a variety of quinoline, quinazoline, phthalazine, and picoline derivatives takes place with simultaneous installation of central and axial chirality, reaching excellent diastereo- and enantiomeric excesses when in situ formed [Pd0/DM-BINAP] was used as the catalyst, with loadings reduced down to 2 mol % in large scale reactions. The coupling of acyclic, electron-rich alkenes can also be performed using a [Pd0/Josiphos ligand] to obtain axially chiral heterobiaryl α-substituted alkenes in high yields and enantioselectivities. Products from Boc-protected 2,3-dihydropyrrole can be easily transformed into N,N ligands or appealing axially chiral, bifunctional proline-type organocatalysts. Computational studies suggest that a β-hydride elimination is the stereocontrolling step, in agreement with the observed stereochemical outcome of the reaction.Ministerio de Ciencia e Innovación (Grants CTQ2016-76908-C2-1-P; CTQ2016-76908-C2-2-P; CTQ2016-78083-P; RYC-2013-12585)European Commission (FEDER Programme)Junta de Andalucía (Grant 2012/FQM 10787)Universidad de Sevilla (Grant No. 1800511201)European Union - Marie Skłodowska-Curie (COFUND—Grant Agreement nº 291780

Los colorantes organoborónicos derivados de arilisoquinolina con un esqueleto de triarilo muestran fluorescencia dual

Se prepararon cuatro nuevos colorantes que derivan de arilisoquinolinas boryiladas, que contienen un tercer residuo de arilo (naftilo, 4-metoxinaftilo, pirenilo o antrilo) que se une a través de un eje estereogénico adicional. Los núcleos de triarilo se sintetizaron mediante acoplamientos Suzuki y luego se transformaron en ésteres de ácido borónico empleando una reacción catalizada por Ir (I). Los cromóforos muestran un comportamiento de emisión dual, donde la banda de emisión de longitud de onda larga puede alcanzar máximos cercanos a 600 nm en solventes polares. Los rendimientos cuánticos de fluorescencia de los colorantes están generalmente en el rango de 0.2-0.4, alcanzando en algunos casos valores tan altos como 0.5-0.6. La fotólisis con flash láser proporcionó evidencia de la existencia de estados triplete excitados. Los colorantes forman complejos de fluoroboronato con aniones fluoruroFour new dyes that derive from borylated arylisoquinolines were prepared, containing a third aryl residue (naphthyl, 4-methoxynaphthyl, pyrenyl or anthryl) that is linked via an additional stereogenic axis. The triaryl cores were synthesized by Suzuki couplings and then transformed into boronic acid esters by employing an Ir(I)-catalyzed reaction. The chromophores show dual emission behavior, where the long-wavelength emission band can reach maxima close to 600 nm in polar solvents. The fluorescence quantum yields of the dyes are generally in the range of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laserflash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and ratiometric response by the build-up of a hypsochromically shifted emission signalSpanish Ministry of Economy, Industry, and Competitiveness (CTQ2014-54729-C2-1-P for U.P., CTQ2013- 48164-C2-1-P and CTQ2013-48164-C2-2-P for A.R.)Spanish Ministry of Science, Innovation, and Universities (CTQ2017-89832-P for U.P., CTQ2016- 78875-P for M.C.J., and CTQ2017-89416-R for I.V.)European Research and Development Fund, and the Andalusian Government (2012/FQM-2140 for U.P., 2009/FQM-4537 and 2012/FQM-1078 for A.R

Excited-State Pathways of Four-Coordinate N,C-Chelate Organoboron Dyes

The excited-state behavior of four-coordinate N,C-chelate organoboron dyes, based on arylisoquinoline ligands with varying degree of charge-transfer character, was characterized. Data related to excited triplet state formation, oxygen quenching, and singlet-oxygen formation were obtained. The results jointly rationalize the previously observed high photostability of the dyes in air-equilibrated media. Furthermore, femtosecond transient absorption experiments enabled the spectroscopic visualization of the excited intramolecular charge transfer (ICT) state that gives rise to the fluorescence of the dyes.The funding by the Spanish Ministry of Economy, Industry, and Competitiveness (grants CTQ2014-54729-C2-1-P for U.P., CTQ2014-54729-C2-2-P for F.B., CTQ2013-48164-C2-1-P, CTQ2013-48164-C2-2-P for A.R., Ramon y Cajal contract RYC-2013-12585 for A.R.), the European Union (ERDF), the Andalusian Government (grants 2012/FQM-2140 for U.P., 2009/FQM-4537 and 2012/FQM-1078 for A.R.), and the University of Huelva (postdoctoral contract for V.F.P.) is gratefully acknowledged