ChemInform Abstract: Reaction of Phosphorus-Stabilized Carbanions with Cyclic Enones. Aromatization of the Substitution and Addition Products (original) (raw)
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Organometallics, 2012
Chloro(organo)phosphines are important precursors to diphosphenes and cyclic oligophosphines. Although chloro(organo)phosphines are commonly reduced with bulk metals (e.g., Na, Mg, and Zn), these reactions are much more selective when done homogeneously. To test whether group 14 heterocarbenoid reductions yield isolable insertion products, the mono-and dichloro(organo)phosphines PhPCl 2 (A), Ph 2 PCl (B), t BuPCl 2 (C), t Bu 2 PCl (D), and bis(dichlorophosphino)methane (PCl 2 ) 2 CH 2 (E) were treated with the cyclic Me 2 Si(μ-N t Bu) 2 El (El = Ge (1), Sn ) and the acyclic [(Me 3 Si) 2 N] 2 El (El = Ge , Sn (4)) heterocarbenoids. The sterically least-encumbered phosphines were more reactive, while the cyclic stannylene 2 was the most reactive and the acyclic germylene 3 was the least reactive. All but one of the products were either mono-or diinsertion compounds, the lone exception being a distannane derived from 2. Semikinetic and structural data suggest that the tetravalent group 14 compounds are formed via an insertion mechanism whose rate depends on the steric bulk of the reaction partners and the nature of the group 14 elements.
Transition metal catalyzed suzuki miyaura reaction
In the transition-metal-catalyzed cross-coupling reactions, the use of the first row transition metals as catalysts is much more appealing than the precious metals owing to the apparent advantages such as cheapness and earth abundance. Within the last two decades, particularly the last five years, explosive interests have been focused on the nickel-catalyzed Suzuki-Miyaura reactions. This has greatly advanced the chemistry of transition-metal-catalyzed cross-coupling reactions. Most notably, a broad range of aryl electrophiles such as phenols, aryl ethers, esters, carbonates, carbamates, sulfamates, phosphates, phosphoramides, phosphonium salts, and fluorides, as well as various alkyl electrophiles, which are conventionally challenging, by applying palladium catalysts can now be coupled efficiently with boron reagents in the presence of nickel catalysts. In this review, we would like to summarize the progress in this reaction. even at room temperature 11 and in a short time, within only several minutes. 12 Moreover, the substrate scope for either coupling partner has been substantially expanded. Typically the electrophiles such as sterically very congested substrates, 11d,13 and the inert aryl and vinyl chlorides 11,14 and sulfonate derivatives, 15 as well as the nucleophiles such as thermally unstable polyfluorophenyl and 2-heteroaryl boron reagents, which are conventionally extremely challenging partners, can now be coupled readily. In addition, the palladium-catalyzed asymmetric Suzuki-Miyaura reaction has also been intensively developed. 17 Moreover, with the rapid development of nanotechnology, considerable progress has been achieved recently by carrying out the reaction in a heterogeneous system by means of anchoring the catalysts onto solid supports with nano size. 18 This development would make the reaction much more sustainable, 19 and, consequently, more practical for industrial applications in terms of the purification of products, as well as the separation, recovery, and reuse of the catalysts. Owing to these important advances, the palladium-catalyzed Suzuki-Miyaura cross-coupling has become the first choice for chemists in a wide range of communities if a C-C bond forming reaction is under consideration. By employing this reaction, almost all kinds of biaryl, aryl-vinyl, alkyl-aryl, and alkyl-alkyl compounds can be synthesized efficiently. Needless to elaborate any further, the importance of the palladiumcatalyzed Suzuki-Miyaura reaction has been well recognized with the 2010 Nobel Prize in chemistry together with Heck and Negishi couplings. Standing on the privileged and well-established platform, synthetic organic chemists have been devoted to the more challenging issues remaining both in industry and academia. To this end, much recent attention in Suzuki-Miyaura crosscoupling has been focused on the nickel catalysts because nickel is much cheaper and more earth abundant than the palladium metal. 22 Therefore, the use of nickel catalysts would be far more cost-effective, unless a coupling reaction is workable with a very low level of palladium loading, or only with a very high nickel catalyst loading. On the other hand, the redox state of palladium is typically Pd (0) /Pd (II) , albeit the catalysis chemistry of high valent palladium such as Pd (III) and Pd (IV) has been increasingly investigated in recent direct C-H functionalization. In contrast, the early transition metal nickel usually displays Ni (0) /Ni (II) as well as Ni (I) /Ni (III) oxidation states and is more nucleophilic due to its smaller size. 24b As such, nickel can not be simply considered to be a substitute for palladium, it possesses distinctive catalytic properties that palladium does not have. Indeed, extensive studies have clearly demonstrated that the nickel-based catalysts were more versatile and powerful catalysts for the C-C, 24 C-N, 24b,c and C-P 25 bond forming reactions of a diverse class of electrophiles, which are conventionally challenging in the presence of palladium catalysts .
New aminomethylphosphines with cyanophenyl substituents at the nitrogen atoms
Russian Chemical Bulletin
A condensation of bis(hydroxymethyl)arylphosphines with 3- and 4-aminobenzonitriles leads to the corresponding 3,7-diaryl-1,5-bis(cyanophenyl)-1,5-diaza-3,7-diphosphacyclooctanes. Acyclic (aryl)bis[N-(2-cyanophenyl)aminomethyl]phosphines are formed in the case of 2-aminobenzonitrile. Molecular and crystalline structure of the compounds obtained was studied by X-ray diffraction analysis.
Tetrahedron, 2000
AbstractÐA variety of new chiral phosphoramidites was synthesised and tested in the copper-catalysed enantioselective conjugate addition of diethylzinc to cyclohexenone and chalcone in order to assess the structural features that are important for stereocontrol. A sterically demanding amine moiety is essential to reach high e.e.'s. Enantioselectivities for chalcones up to 89% and for cyclic enones up to 98% were found. Studies on non-linear effects with the best ligands for both cyclohexenone and chalcone showed clear non-linear effects for both cyclic and acyclic enones. q
European Journal of Inorganic Chemistry, 2009
The reaction of 3-ferrocenyl-substituted 2H-azaphosphirene complexes 1a-c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5-diferrocenylsubstituted 2H-1,4,2-diazaphosphole complexes 3a-c and difluoro(organo)phosphane complexes 4a-c. The reaction of 1a,c and [FcH]PF 6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single-crystal Xray diffraction studies. DFT calculations on model complexes
European Journal of Medicinal Chemistry, 2006
As a part of the research on the improvement of an alternative to conventional photodynamic therapy by light-induced formation of intercalators, we synthesized a series of novel heterocyclic compounds and their acyclic precursors. We now report details about their synthesis/ characterization in respect to their potential of photoinduced cyclization, interactions with DNA and inhibition of the tumor cell growth in vitro. Among studied compounds only amidino-furyl-substituted phenyl acrylates were efficiently converted to the corresponding naphthofuranes, while their thiophene analogues, all non-charged derivatives and amidino-phenyl-substituted analogues didn't show acceptable photoconversion. The significantly stronger antiproliferative activity of cyclic analogues could be correlated to the property of these molecules to intercalate into DNA. The acyclic molecules did not show any interaction with DNA, correlating with the inferior biological activity, except for one cyanobearing molecule.