Palladium-catalyzed three-component coupling of arynes with allylic acetates or halides and terminal alkynes promoted by cuprous iodide

Benzynes react with allylic acetates or halides and terminal alkynes in the presence of Pd(PPh3)4, CuI and CsF in CH3CN at 50 degrees C for 5 h to give 1-allyl-2-alkynylbenzene derivatives in good to excellent yields.     

Ruthenium‐Catalyzed Oxidant‐Free Allylation of Aromatic Ketoximes with Allylic Acetates at Room Temperature

Substituted aromatic ketoximes reacted efficiently with allylic acetates in the presence of {[RuCl₂(p‐cymene)]₂} and AgSbF₆ in 1,2‐dichloroethane at ambient temperature, providing ortho‐allyl aromatic ketoximes in a highly regioselective manner without an oxidant. In the reaction, the acetate group of allyl acetate acts as a base to activate the C?H bond of aromatics. Later, ortho‐allyl aromatic ketoximes were converted into ortho‐allyl aromatic ketones in the presence of HCl.     

Regioselective synthesis of isocoumarins by ruthenium-catalyzed aerobic oxidative cyclization of aromatic acids with alkynes

The highly regioselective aerobic oxidative cyclization of aromatic, heteroaromatic and alkenyl acids with alkynes in the presence of catalytic amounts of [{RuCl(2)(p-cymene)}(2)], AgSbF(6) and Cu(OAc)(2)·H(2)O providing isocoumarin derivatives was investigated.     

Role of dipole moment of solvents in formation and stabilization of the TICT states in Coumarin 445 under nitrogen laser excitation

In this paper we report the observation of dual Amplified Spontaneous Emission (ASE) from solutions of 7-ethylamino-4-methyl coumarin dye (Coumarin 445) in certain solvents such as n-butyl acetate, dioxane etc. when pumped by high power nitrogen laser. The two ASE bands appear to be from two different excited species (ICT and TICT conformation) one of which is the precursor of the other. The spectral characteristics of dye Coumarin 445 depend upon the solvent environment. The TICT coumarin photoisomers, which form exciplexes with the solvent molecules, have enough gain to produce amplified spontaneous emission even when there is apparently no detectable fluorescence. The behaviour of this dye in the excited state is studied by measuring the small signal gain and variation of the gain slope with temperature in different solvents. It is observed that polarity of the solvent plays a more dominant role in formation and stabilization of TICT states.     

Ruthenium-catalyzed highly regioselective cyclization of ketoximes with alkynes by C-H bond activation: a practical route to synthesize substituted isoquinolines

Aromatic and heteroaromatic ketoximes underwent cyclization with alkynes in the presence of a catalytic amount of [{RuCl(2)(p-cymene)}(2)] and NaOAc to give isoquinoline derivatives in good to excellent yields in a highly regioselective manner.     

The laser gain characteristics of some substituted coumarins

A theoretical and experimental study has been made of the small signal gains of six coumarin dyes (DAMC, 4 MU, 7 HC, calcein blue, esculin and scopoletin) in a common solvent (ethanol), and the variation correlated with the different substituents in the coumarins. The relative variation in gain, taking the value for DAMC as the basis, is about 75% for 4 MU, 7 HC and calcein blue, 55% for esculin and 20% for scopoletin. The total tunable range for these dyes is from 430–530 nm. The higher gain in the case of DAMC is attributed to the relatively higher intramolecular charge transfer in this dye compared to the hydroxy-coumarins. The different substituents in the hydroxy-coumarins studied appear to have only a marginal influence on the gain.     

Solvent effects on the spectral and gain characteristics of a DAMC dye laser

Small signal gains of a 7-diethylamino 4-methyl coumarin (DAMC) dye laser in a variety of solvent environments have been experimentally determined from the super-radiant emission of these dye solutions. The study suggests that polar, hydrogen-bonding solvents appear to be most suitable for producing high gain in the DAMC dye laser.     

Highly efficient route to o-Allylbiaryls via palladium-catalyzed three-component coupling of benzynes, allylic halides, and aryl organometallic reagents

[reaction: see text] o-Allylbiaryl derivatives have been prepared in good to excellent yields by the palladium-catalyzed three-component reaction of allyl halides, benzynes, and aryl organometallic reagents.     

Cobalt- and nickel-catalyzed regio- and stereoselective reductive coupling of alkynes, allenes, and alkenes with alkenes

Transition-metal-catalyzed coupling of two different C-C pi components through a metallacycle intermediate is a highly atom economical method to construct C-C bonds in organic synthesis. The metal-catalyzed coupling of an alkene and alkyne generally gives an Alder-ene or reductive coupling product. In this article, we focus on the cobalt- and nickel-catalyzed reductive coupling of alkynes, allenes, and alkenes with alkenes. These reductive coupling reactions provide convenient methods for the synthesis of various alkenes, dienes, functionalized alkanes, lactones, lactams, and cyclic alcohols in a highly regio- and stereoselective manner. A chemselective formation of metallacyclopentene intermediate from the two different C-C pi components and a low-valence metal species plays a key role for the high regio- and stereoselectivity of the catalytic reaction.     

Spectral and laser gain characteristics of solvated species of scopoletin

This paper reports the spectral and small signal laser gain characteristics of various solvated species of scopoletin. The spectra show that a methoxy substituent in the sixth position of 7-hydroxy coumarin precludes the formation of excited state tautomers and leads to a large overlap of the fluorescence bands of various species. This is also reflected in the gain, and the total gain bandwidth of scopoletin is small compared to that obtainable in 4 MU or 7 HC, utilizing the solvation characteristics of these dyes.