- Synthesis and Catalytic Use of Gold(I) Complexes Containing a Hemilabile Phosphanylferrocene Nitrile Donor
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Removal of the chloride ligand from [AuCl(1-κP)] (2) containing a P-monodentate 1′-(diphenylphosphanyl)-1-cyanoferrocene ligand (1), by using silver(I) salts affords cationic complexes of the type [Au(1)]X, which exist either as cyclic dimers [Au(1)]2X2 (3a, X=SbF6; 3 c, X=NTf2) or linear coordination polymers [Au(1)]nXn (3 a′, X=SbF6; 3 b′, X=ClO4), depending on anion X and the isolation procedure. As demonstrated for 3 a′, the polymers can be readily cleaved by the addition of donors, such as Cl-, tetrahydrothiophene (tht) or 1, giving rise to the parent compound 2, [Au(tht)(1-κP)][SbF6] (5 a) or [Au(1-κP)2][SbF6] (4 a), respectively, of which the last two compounds can also be prepared by stepwise replacement of tht in [Au(1-κP)2][SbF6]. The particular combination of a firmly coordinated (phosphane) and a dissociable (nitrile) donor moieties renders complexes 3/3′ attractive for catalysis because they can serve as shelf-stable precursors of coordinatively unsaturated AuI fragments, analogous to those that result from the widely used [Au(PR3)(RCN)]X catalysts. The catalytic properties of the Au-1 complexes were evaluated in model annulation reactions, such as the synthesis of 2,3-dimethylfuran from (Z)-3-methylpent-2-en-4-yn-1-ol and oxidative cyclisation of alkynes with nitriles to produce 2,5-disubstituted 1,3-oxazoles. Of the compounds tested (2, 3 a′, 3 b′, 3 a, 4 a and 5 a), the best results were consistently achieved with dimer 3 c, which has good solubility in organic solvents and only one firmly bound donor at the gold atom. This compound was advantageously used in the key steps of annuloline and rosefuran syntheses.
- ?koch, Karel,Císa?ová, Ivana,?těpni?ka, Petr
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supporting information
p. 15998 - 16004
(2015/11/03)
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- Wittig Olefination Using Phosphonium Tetraphenylborate in the Absence of Additional Base
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The thermal decomposition of (substituted methyl)triphenylphosphonium tetraphenylborates, which can also be generated in situ from the corresponding phosphonium halide and NaBPh4, with an aldehyde affords olefins in 22-100% yields. This Wittig olefination does not need use additional base to form phosphorus ylide, and is highly tolerant of benzoic acid.
- Huang, Wenhua,Zhao, Shuang-Hong,Dong, Guang-Ping
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supporting information
p. 1802 - 1810
(2015/10/29)
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- Total synthesis of (+)-virgatusin via AlCl3-catalyzed [3+2] cycloaddition
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The AlCl3-catalyzed cycloaddition of a donor-acceptor (don-acc) cyclopropane and piperonal succinctly provides the core of virgatusin in a selective, high-yielding manner. The Royal Society of Chemistry 2009.
- Sanders, Shanina D.,Ruiz-Olalla, Andrea,Johnson, Jeffrey S.
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supporting information; experimental part
p. 5135 - 5137
(2009/12/08)
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- TOTAL SYNTHESIS OF SCELETIUM (AIZOACEAE) ALKALOIDS. THE CINNAMONITRILE ROUTE. THE TOTAL SYNTHESIS OF RACEMIC O-METHYL JOUBERTIAMINE AND MESEMBRINE
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A new method of synthesis of Sceletium (Aizoaceae) alkaloids based on the introduction of a "formyl anion" equivalent at the β-position of a cinnamonitrile, followed by Robinson annulation and final modification of the resulting cyanomethyl side is described.The method has been succesfully applied to the total synthesis of racemic O-methyljoubertiamine (1) and mesembrine (2).
- Sanchez, Ignacio H.,Tallabs, F. Ramon
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p. 891 - 894
(2007/10/02)
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