We present a theoretical and experimental study of the structure and NMR parameters of the pentacarbonyltungsten complexes of η
A new Negishi type cross-coupling of 2-bromophosphinine has been developed. The new method expands the scope of palladiumcatalysed couplings to monobromophosphinines, which have been considered as poor substrates so far. Moreover, aryl-, alkenyl-and alkynylzinc bromides were found to be effective coupling partners. IntroductionTransition metal catalysis is a powerful tool in organic synthesis as illustrated by the wealth of reactions that rely on the activation by metal complexes. The ligand on the metal is a crucial component in this chemistry as it controls the reactivity of the catalyst towards specific substrate classes and the stereochemistry of the process. As such, the development of new ligand systems that impose novel and unique reactivity/selectivity profiles is a major goal of the field. Phosphinines [1] , the higher homologues of pyridines, are planar, aromatic phosphorous-containing heterocycles with unique electronic, steric and coordination properties, which make them attractive scaffolds for ligand development. The first reports of 1λ 3 -phosphinines, appeared in the late 1960`s. [2] Although they are isoelectronic to pyridines, they exhibit quite different electronic properties. Spectroscopic and theoretical investigations indicate that phosphinines are better π-acceptor ligands, but less σ-donating, than pyridines. [3] Due to their unusual properties, the application of functionalized phosphinines as ligands in homogenous catalysis has received considerable interest. [1b, c, 4] The most successful strategies for the synthesis of complex phosphinine-containing structures are based on pyryllium salts [5] or 1,3,2-diazaphosphinines [6] as precursors. Alternatively, a number of methods for the functionalization of preformed phosphinines [1a] are known, such as direct bromination [7] , phosphination [8] , ethylation [9] and transformations of 2-metallated phosphinines (M = Li [10] , Mg [7] , Zn [10c-e, 11] and Zr [1a, 12] ). A major limitation of these methods is the lack of versatility with respect to the groups that can be introduced. However, Mao and Mathey recently introduced an interesting, functionalisable phosphinine building block when a phosphinine-2-carboxaldehyde was transformed into an alkene via a Wittig reaction. [13] In 1993, Le Floch et al. described the palladium(0)-catalyzed cross-coupling with organotin reagents. [14] They were able to couple polybromophosphinines with trimethyltin derivatives of furan, N-methylpyrrole, thiophene and phenylacetylene using Pd(dba) 2 and monodentate phosphines e. g. triphenylphosphine or tri-2-furylphosphine as the catalyst system. However, they discovered that mono-and dibromophosphinines were much poorer substrates for the Stille coupling. For example, the alkynylation of monobromophosphinines with trimethyl(2-phenylethynyl)stannane could not be achieved. Clearly, the incorporation of the phosphinine core into more complex structures still remains a synthetic challenge.During our efforts to explore phosphinines as potential ligands in...
Palladium(0)-Catalyzed Cross-Couplings of 2-Bromophosphinine. -The new title Negishi-type cross-coupling reaction expands the scope of monobromophosphines, which are considered as poor substrates so far. Aryl-, alkenyl-, and alkynylzinc bromides are effective coupling partners. -(KOSTENKO, N.; ERICSSON, C.; ENGQVIST, M.; GONZALEZ, S. V.; BAYER*, A.; Eur. J. Org. Chem. 2013, 22, 4756-4759, http://dx.
Abstract. The cooperation among the states requires that countries adapt their strategies to new terms of interaction when concluding regional trade agreements. Integration priorities are aimed at improving nations' welfare and national competitiveness. The purpose of the article is to identify the areas of economic adaptation based on the world ranking and matrix of geoeconomic strategies development. The matrix being proposed helps countries to identify development strategies in bilateral cooperation and to find the ways to improve trade infrastructure. Descriptive statistics method and index method are used in the article.
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