[Show abstract][Hide abstract] ABSTRACT: A strategy for the construction of spiro[cycloalkane-1,3′-1′λ6-isothiazolidine]-1′,1′,4′-triones through the sulfonylation of 1-aminocyclopropane- and 1-aminocyclobutanecarboxylates with methanesulfonyl chloride followed by alkylation with methyl iodide and subsequent cyclization in the presence of potassium tert-butoxide in N,N-dimethylformamide is reported. An efficient synthesis of starting 1-aminocyclopropane- and 1-aminocyclobutanecarboxylic acids was developed. The reaction of spiro[cycloalkane-1,3′-1′λ6-isothiazolidine]-1′,1′,4′-triones with N,N-dimethylformamide dimethyl acetal (DMF-DMA) gives 5′-[(Z)-(dimethylamino)methylene]spiro[cycloalkane-1,3′-1′λ6-isothiazolidine]-1′,1′,4′-triones, the structure of which was confirmed by X-ray diffraction study.
[Show abstract][Hide abstract] ABSTRACT: Bi-directional syntheses of C2-symmetrical lipids embedding two terminal alkynylcarbinol pharmacophores are reported. Naturally occurring chiral alkenyl-alkynylcarbinol units were generated using the Pu?s procedure for enantioselective addition of terminal alkynes to aldehydes, allowing the first asymmetric synthesis of (3R,4E,16E,18R)-icosa-4,16-diene-1,19-diyne-3,18-diol, isolated from Callyspongia pseudoreticulata. Two synthetic analogues embedding the recently uncovered (S)-dialkynylcarbinol pharmacophore were secured using the Carreira?s procedure adapted to ynals. The dramatic effect of chiral configuration on the cytotoxicity of these derivatives was confirmed with submicromolar IC50 against HCT116 cells.
The Journal of Organic Chemistry 05/2015; 80(11). DOI:10.1021/acs.joc.5b00494 · 4.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two new zinc-terephthalate MOFs, (H2NEt2)[Zn3(BDC)3(HCO2)]•1.5DEF (1) and Zn4(BDC)3(HCO2)2(DEF)4 (2), based on trinuclear zinc secondary building units have been solvothermally synthesized from the well-studied MOF-5 system Zn–H2BDC–DEF (H2BDC = 1,4-benzenedicarboxylic acid or terephthalic acid; DEF = N,N-diethylformamide). It is shown that adding small amounts of formic acid to this system has a great influence on the formation of 3D networks based upon trimetallic zinc building units Zn3(O2CR)6. The structures of 1 and 2 comprise stacked 36 tessellated 2D zinc-terephthalate layers which are linked into 3D frameworks either by bridging formate monoanions (1) or by in situ generated neutral bridging units Zn(HCO2)2(DEF)4 (2). Flowing supercritical-CO2 activation of 1 led to a partially (∼80%) desolvated and probably collapsed structure (1-SC) with a measured BET (Brunauer–Emmett–Teller) surface area of 38 m2.g-1.
[Show abstract][Hide abstract] ABSTRACT: A systematic study of carbo-butadiene motifs not embedded in an aromatic carbo-benzene ring is described. Dibutatrienylacetylene (DBA) targets R(1) C(R)CCC(Ph)C≡CC(Ph)CCC(R)R(2) are devised, in which R is C≡CSiiPr3 and R(1) and R(2) are R, H, or 4-X-C6 H4 , with the latter including three known representatives (X: H, NMe2 , or NH2 ). The synthesis method is based on the SnCl2 -mediated reduction of pentaynediols prepared by early or late divergent strategies; the latter allows access to a OMe-NO2 push-pull diaryl-DBA. If R(1) and R(2) are H, an over-reduced dialkynylbutatriene (DAB) with two allenyl caps was isolated instead of the unsubstituted DBA. If R(1) =R(2) =R, the tetraalkynyl-DBA target was obtained, along with an over-reduced DBA product with a 12-membered 1,2-alkylidene-1H2 ,2H2 -carbo-cyclobutadiene ring. X-ray crystallography shows that all of the acyclic DBAs adopt a planar trans-transoid-trans configuration. The maximum UV/Vis absorption wavelength is found to vary consistently with the overall π-conjugation extent and, more intriguingly, with the π-donor character of the aryl X substituents, which varies consistently with the first (reversible) reduction potential and first (irreversible) oxidation peak, as determined by voltammetry.
Chemistry - A European Journal 01/2014; 20(2). DOI:10.1002/chem.201303169 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We recently disclosed the synthesis of a novel "push-pull" boryl(phosphino)carbene. To determine the influence of this substitution pattern on the chemical behaviour, a study into the reactivity of the prototype (1) of this new family of B(sp(2) )-substituted phosphinocarbenes was undertaken. Carbene 1 exhibits one of the most common intramolecular rearrangements of singlet carbenes, involving a 1,2-mesityl shift, and typical [2+1] cycloaddition reactions with electron-poor acrylonitrile. A pronounced α,β-ambiphilic character was also shown by the reaction of 1 with benzaldehyde, leading to phosphorylalkene 4. Due to its specific electronic properties, carbene 1 also exhibits unprecedented reactivity with chloroacrylonitrile, enabling the formation of bicyclo[1.1.0]phosphetanium salt 6 and borylcyclopropene 9, which have been fully characterised by NMR spectroscopy and X-ray crystallography.
Chemistry - A European Journal 01/2014; 20(1). DOI:10.1002/chem.201303039 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Keen to donate: A stable and isolable silene with two π-donating groups on the silicon center has been synthesized. This silicon-substituted silene shows totally different π-substituent effects compared to those of related carbon-substituted silenes, and it presents intrinsic silene properties with an enhanced electron-donating character, making it an excellent ligand for transition metals.
[Show abstract][Hide abstract] ABSTRACT: A stable base-stabilized sila-β-lactone was successfully synthesized and fully characterized. Interestingly, this sila-β-lactone shows a very unique reactivity toward ethanol, leading to the formation of an isolable donor/acceptor-stabilized silanoic acid.
[Show abstract][Hide abstract] ABSTRACT: The synthesis, structure, and absorption spectra of highly π-frustrated carbo-benzenes with indolic enamine substituents more or less directly conjugated to the C18 macro-aromatic core are described, and their peculiar reactivity is analyzed.
Chemical Communications 08/2013; 49(75). DOI:10.1039/c3cc43204a · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Insertion without assertion: Alkenes reacted reversibly under mild conditions (25-85 °C) with phosphine-silylene complexes containing a Si(II) Sn bond to give alkyl silylene complexes. Theoretical studies indicated that the insertion reaction proceeds through oxidative addition and migratory insertion in a two-step process and thus revealed that silicon(II)-phosphine complexes can behave like transition-metal complexes.
[Show abstract][Hide abstract] ABSTRACT: As intriguing as the Bermuda Triangle: The synthesis and characterization of an isolable silacyclopropan-1-one (see structure; red O, blue N, green Si, yellow P) was made possible by stabilization through intramolecular coordination by a Lewis base. However, this silacyclopropan-1-one, which contains a significantly elongated endocyclic CC σ bond, remains highly reactive and underwent an unprecedented silanone-silenol rearrangement under mild conditions.
[Show abstract][Hide abstract] ABSTRACT: The synthesis and characterization of chlorogermylenes and (diazomethyl)germylenes involving the germanium atom coordinated to a tungsten pentacarbonyl group are reported. Treatment of chlorogermylene 1 with pentacarbonyl(tetrahydrofuran) tungsten led to chlorogermylene complex 2 in good yield. A similar reaction with (diazomethyl)germylene 3 gave complex 4, which rapidly lost the trimethylsilyl moiety to generate tungsten complex 5. Otherwise, complex 5 was obtained directly by reaction of the lithium salt of trimethylsilyldiazomethane with complex 2. Complexes 2 and 5 were fully characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography. The photolysis of 5 was studied with the aim of generating a germa-alkyne complex.
European Journal of Inorganic Chemistry 12/2012; 2012(35):5771-5775. DOI:10.1002/ejic.201200891 · 2.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The first examples of a novel family of sp-carbon-rich n-π-conjugated oligomers/polymers, namely carbo-mers of polyacetylene, also referred to as "1,4-PTA" isomers of the classical polytriacetylenes (1,2-PTAs), are described in the perphenylated series. The two first representatives proved to be stable in solution, and exhibit a zig-zag arrangement in the crystal state. The third member of the family, isolated in SnCl(2) matrix, proved to be stable in the solid state and was characterized by MALDI-TOF MS, (1) H NMR, CPMAS (13) C NMR, and absorption spectroscopy. An explanation for its reactivity in solution is proposed. The chromophoric properties in the visible region are shown to vary significantly and consistently along the series.
Chemistry - A European Journal 11/2012; 18(46). DOI:10.1002/chem.201201555 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A series of stable quadrupolar bis(p-aminophenyl)-carbo-benzenes, featuring both donor-donor-donor π-frustration and central macro-aromaticity, is described and compared to the acyclic dibutatrienylacetylene (DBA) reference series.
Chemical Communications 07/2012; 48(70):8763-5. DOI:10.1039/c2cc34176j · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The reaction of phosphine-stabilized germylenes (1a,b) with dimer complex [Rh(2)(μ-Cl)(2)(COD)(2)] leads to the corresponding phosphine-germylene-Rh(I) complexes (2a,b). Interestingly, the stability of these complexes depends strongly on the nature of the substituent of the germylene fragment. Indeed, the complex (2a) with the chloro-germylene ligand isomerizes into a metallacycle rhodium complex (3a) via germylene insertion into the Rh-Cl bond, while the complex with the phenyl-substituted germylene (2b) was isolated and represents the first stable Rh(I)-germylene complex with a Rh-Cl bond.
[Show abstract][Hide abstract] ABSTRACT: Strained but stable: An isolable silacycloprop-1-ylidene stabilized by intramolecular complexation with an iminophosphorus ylide fragment was successfully synthesized and fully characterized. The formation of this small highly strained cyclic silylene involves an unprecedented Si(IV)→Si(II) rearrangement under very mild conditions.
[Show abstract][Hide abstract] ABSTRACT: When targeting the quadrupolar p-dianisyltetraphenyl-carbo-benzene by reductive treatment of a hexaoxy-pericyclyne precursor 3 with SnCl(2)/HCl, a strict control of the conditions allowed for the isolation of three C(18)-macrocyclic products: the targeted aromatic carbo-benzene 1, a sub-reduced non-aromatic carbo-cyclohexadiene 4A, and an over-reduced aromatic dihydro-carbo-benzene 5A. Each of them was fully characterized by its absorption and NMR spectra, which were interpreted by comparison with calculated spectra from static structures optimized at the DFT level. According to the nucleus-independent chemical shift (NICS) value (NICS≈-13 ppm), the macrocyclic aromaticity of 5A is indicated to be equivalent to that of 1. This is confirmed by the strong NMR spectroscopic deshielding of the ortho-CH protons of the aryl substituents, but also by the strong shielding of the internal proton of the endocyclic trans-CH=CH double bond that results from the hydrogenation of one of the C≡C bonds of 3. Both the aromatics 1 and 5A exhibit a high crystallinity, revealed by SEM and TEM images, which allowed for a structural determination by using an X-ray microsource. A good agreement with calculated molecular structures was found, and columnar assemblies of the C(18) macrocycles were evidenced in the crystal packing. The non-aromatic carbo-cyclohexadiene 4A is shown to be an intermediate in the formation of 1 from 3. It exhibits a remarkable dichromism in solution, which is related to the occurrence of two intense bands in the visible region of its UV/Vis spectrum. These properties could be attributed to the dibutatrienylacetylene (DBA) unit that occurs in the three chromophores, but which is not involved in a macrocyclic π-delocalization in 4A only. A versatile redox behavior of the carbo-chromophores is evidenced by cyclic voltammetry and was analyzed by calculation of the ionization potential, electron affinity, and frontier molecular orbitals.
Chemistry - A European Journal 03/2012; 18(11):3226-40. DOI:10.1002/chem.201102993 · 5.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dismembering molecules: The stable boryl(phosphino)carbene 1 can cleave small organic dioxide molecules. With CO(2) and SO(2) , 1 gives, respectively, the phosphacumulene ylide [Mes(iPr(2) N)B-O-P(CCO)(NiPr(2) )Mes] (see scheme and structure) and boryl(phosphoryl)sulfine [Mes(iPr(2) N)B-C(SO)-P(O)(NiPr(2) )Mes] which have been structurally and spectroscopically characterized.