Conclusion It was found that the strong electron acceptor-donor chromophoric system of these compounds showed high Stoke's shift and excellent thermal stability. Compounds showed positive solvatofluorism behavior from nonpolar to polar solvent. All compounds have good thermal stability. Background Organic fluorescent heterocyclic chromophores have a wide range of applications in molecular probes [ 1 ], fluorescent markers [ 2 ], organic light-emitting diodes OLED [ 3 ], photovoltaic cells [ 4 ] and in traditional textile and polymer fields [ 5 ].
Electron donors like triphenylamine [ 6 ], diphenylamine [ 7 ] 1,3,5-triazines [ 8 ] and carbazoles [ 9 ] with high electron mobility, thermal and photochemical stability are commonly used as hole-transporting materials or light-emitting materials for balanced charge injection for above mentioned application.
N,N-Dialkyl substituted 1,3,5-triazine fluorescent styryl derivatives have not been exploited much in the past, but attract increasing interest as they exhibit better solubility in common organic solvents, excellent thermal and electron donating ability of N,N-alkyl groups. The presence of electron donating N,N-dialkyl group increases the electron flow towards the electron acceptor moieties present in the molecules.
If L is a ligand comprising only one double bond, e. A rhodium complex catalyst can be prepared, for example, by reaction of rhodium precursors such as e. Sac, , 93, p. Jacobsen, A. Pfaltz, H.
In the ruthenium complex catalysts referred to above, ruthenium is characterised by the oxidation number II. Such ruthenium complexes can optionally comprise further ligands, either neutral or anionic. Suitable ruthenium complexes in question can be represented e. These complexes can in principle be manufactured in a manner known per se, e.
Heiser et al. Feiken et al. Genet, Acc. Fleming et al. Conveniently and preferably, ruthenium complexes are manufactured, for example, by reacting a complex of the formula [Ru Z1 2 L 1 m]p.
H2O q wherein Z1 represents halogen or a group A1-COO, A1 represents lower alkyl or halogenated lower alkyl, L1 represents a neutral ligand as defined above, m represents the number 1, 2 or 3, p represents the number 1 or 2 and q represents the number 0 or 1, with a chiral diphosphine ligand. Where m represents the number 2 or 3, the ligands can be the same or different.
Rhodium, iridium or ruthenium complex catalysts as described above can also be prepared in situ, i. The solution in which such a catalyst is prepared can already contain the substrate for the enantioselective hydrogenation or the solution can be mixed with the substrate just before the hydrogenation reaction is initiated.
The asymmetric hydrogenation of a compound of formula II according to the present invention takes place at a hydrogen pressure in a range from 1 bar to bar. Preferably, the asymmetric hydrogenation is carried out at a pressure of 10 to 40 bar. This reaction can be effected in an inert organic solvent such as tetrahydrofuran, ethanol and 2,2,2-trifluoroethanol, or mixtures of 2,2,2-trifluorethanol with other solvents such as dichloromethane, methanol, ethanol, n-propanol, isopropanol, benzotrifluoride Ph-CF3 , tetrahydrofuran, ethyl acetate or toluene.
Preferably, the rhodium catalyzed hydrogenation is carried out in 2,2,2-trifluoroethanol. The ruthenium catalyzed hydrogenation is carried out in a solvent taken from the group consisting of 2,2,2-trifluoroethanol, methanol, ethanol, n-propanol and dichloromethane, or mixtures of these solvents. More preferably, the ruthenium catalyzed hydrogenation is carried out in 2,2,2-trifluoroethanol. The amount of catalyst used in the process of the present invention is in the range of 20 to 0.
The process of the present invention can be carried out in the presence of an additive. Suitable additives include inorganic or organic salts and organic bases. Examples of salts are ammonium acetate, caesium carbonate, sodium formiate and sodium phosphate. Organic bases include a secondary or a tertiary amine such as for example dicyclohexylamine, diisopropylethylamine and triethylamine.
Each of these bases may be used alone, or as a mixture of two or more kinds of them. The amount of base used is appropriately selected usually from the range of 0.
Suitable amino protecting groups and its introduction are described in Green T. Suitable amino protecting groups are trichloroethoxycarbonyl, benzyloxycarbonyl Cbz , chloroacetyl, trifluoroacetyl, phenylacetyl, formyl, acetyl, benzoyl, tert-butoxycarbonyl Boc , para-methoxybenzyloxycarbonyl, diphenylmethoxycarbonyl, phthaloyl, succinyl, benzyl, diphenylmethyl, triphenylmethyl trityl , methanesulfonyl, para-toluenesulfonyl, pivaloyl, trimethylsilyl, triethylsilyl, triphenylsilyl, and the like, whereby tert-butoxycarbonyl Boc is preferred.
Introduction of the amino protecting group can be effected following procedures well known to the skilled in the art. Alternatively, steps a and b can be carried out together in one reactor without isolation of the compounds of formula IIIa or IIIb. Preferably, a solution of Boc2O in 2,2,2-trifluoroethanol is added continuously during the hydrogenation by pump. In a preferred embodiment step b comprises the manufacture of ester IV, wherein R2 and R3 are methoxy, R4 is hydrogen and R1 and Prot are as defined before.
Most preferably, R1 is ethyl.Jump to Scheme 10 An efficient approach  for the preparation of unsymmetrical ethers from alcohols has been developed by utilizing NaAuCl4. However, a significant improvement of reaction efficiency was observed by employing alcohol substrates bearing coordination functionalities. As with gold-catalyzed C—O bond formation, the directly catalytic addition of a nitrogen nucleophile to a C—C multiple bond represents an attractive approach to the formation of C—N bonds . Jump to Scheme 27 The ring expansion of cyclopropane derivatives provides a powerful method to construct synthetically useful four-membered carbocycles.
Water was added to this solution and the aqueous phase was extracted with 50 ml of diethyl ether three times. Only the most important recent studies have been selected to demonstrate the significance of gold catalysis.
Benzochromanes were obtained when AuCl3 was employed as the catalyst, whereas benzobicyclo[5. Jump to Scheme 17 Dual-catalyzed rearrangement reactions have been reported by Shi and co-workers for the preparation of substituted butenolides and isocoumarins . Although various research efforts have led to gold-catalyzed addition reactions, the area of asymmetric addition has only recently been pioneered.
Yield: 0. The cyclization occurs exclusively in an endo-fashion under mild conditions and provides access to dihydrodioxepines and tetrahydrooxazepines.
A tandem cyclization mechanism was proposed by the authors. Where m represents the number 2 or 3, the ligands can be the same or different.
This glycosylation protocol was used in an efficient synthesis of a cyclic triterpene tetrasaccharide 74, which demonstrated its versatility and efficacy. The gold clusters 0. The counter electrode preferably has conductivity, and functions as a catalyst for the reduction of oxidation-reduction electrolyte. Jump to Scheme 17 Dual-catalyzed rearrangement reactions have been reported by Shi and co-workers for the preparation of substituted butenolides and isocoumarins . The enamine of formula II can be synthesized from commercially available precursors according to the scheme 1 below. Scheme Gold-catalyzed glycosylation.
Preferred salts with acids are formates, maleates, citrates, hydrochlorides, hydrobromides and methanesulfonic acid salts, with hydrochlorides being especially preferred. The catalyst of the present invention can used in any type of solvent, and especially can be used in water, a water-soluble organic solvent or a mixture of these. And, the dye of the present invention can be mixed with other dyes or metal complex dyes. Coupling yields the hydroxymethyl derivative of the pyrido[2,1-a]isoquinoline VIII , which can then subsequently be cyclized to the fluoromethyl-pyrrolidinone derivative IX. This intramolecular piperidine cyclization methodology shows different reactivity and substrate applicability compared with the former intermolecular nucleophilic addition.
Water 30ml and brine were added to the mixed solution. The mixture was refluxed for 22 h. This is a direct and efficient procedure for the synthesis of nitrogen containing compounds of industrial importance.
The present inventors have developed a polymer incarcerated Lewis acid metal catalyst to make it possible to recover the catalyst by incarcerating a Lewis acid metal in a polymer to immobilize it on a carrier or to link it to a network while maintaining the functions of the Lewis acid metal catalyst References 1 and 2.