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Here we report a contractive synthesis of multisubstituted cyclobutanes containing multiple stereocenters from readily accessible pyrrolidines using iodonitrene chemistry. Mediated by a nitrogen extrusion process, the stereospecific synthesis of cyclobutanes involves a radical pathway. Unprecedented unsymmetrical spirocyclobutanes were prepared successfully, and a concise, formal synthesis of the cytotoxic natural product piperarborenine B is reported.

The metalation of N,N-dimethylaminomethylferrocene in THF by the superbasic mixture of

In dynamic covalent chemistry, reactions follow a thermodynamically controlled pathway through equilibria. Reversible covalent‐bond formation and breaking in a dynamic process enables the interconversion of products formed under kinetic control to thermodynamically more stable isomers. Notably, enantioselective catalysis of dynamic transformations has not been reported and applied in complex molecule synthesis. We describe the discovery of dynamic covalent enantioselective metal‐complex‐catalyzed 1,3‐dipolar cycloaddition reactions. We have developed a stereodivergent tandem synthesis of structurally and stereochemically complex molecules that generates eight stereocenters with high diastereo‐ and enantioselectivity through asymmetric reversible bond formation in a dynamic process in two consecutive Ag‐catalyzed 1,3‐dipolar cycloadditions of azomethine ylides with electron‐poor olefins. Time‐dependent reversible dynamic covalent‐bond formation gives enantiodivergent and diastereodivergent access to structurally complex double cycloadducts with high selectivity from a common set of reagents., A highly enantioselectively catalyzed dynamic covalent one‐pot‐tandem 1,3‐dipolar cycloaddition of azomethine ylides to α′‐alkylidene‐2‐cyclopentenones is described. Time‐dependend enantio‐ and diastereodivergent synthesis was achieved by using the same set of reagents. A reversible cycloaddition of the kinetically favored product enables the interconversion to its more stable thermodynamically favored product through a chiral complex‐mediated process.

Insights gained from a comparison of aminometalation reactions with lithium amides, potassium amides and mixed lithium/potassium amides are presented. A combination of structural characterization, DFT calculations and electrophile reactions of aminometalated intermediates has shown the advantages of using a mixed metal strategy. While potassium amides fail to add, the lithium amides are uncontrollable and eliminated, yet the mixed K/Li amides deliver the best of both systems. Aminopotassiation proceeds to form the alkylpotassium species which has enhanced stability over its lithium counterpart allowing for its isolation and thereby its further characterization., The use of a mixed‐metal system consisting of LiNR2/KOR increases the selectivity of the aminometalation of styrene derivatives in favour of a potassiated intermediate over a polymerization product. Crystal structures along with quantum chemical calculations and experimental investigations demonstrate the additional advantages of potassium over lithium or sodium for the stability of metalated phenylethylamines.

The complete mol­ecule of the hexa­metallic title complex, namely, tetra­bromido­tetra-μ-hydroxido-hexa­kis­[μ-2-methyl-3-(pyrrolidin-1-yl)propan-2-olato]hexa­zinc(II) acetone disolvate, is generated by a crystallographic centre of symmetry. Two of the unique zinc atoms adopt distorted ZnO2NBr tetra­hedral coordination geometries and the other adopts a ZnO3N tetra­hedral arrangement. Both unique alkoxide ligands are N,O-chelating and both hydroxide ions are μ2 bridging., The complete mol­ecule of the hexa­metallic title complex, namely, tetra­bromido­tetra-μ-hydroxido-hexa­kis­[μ-2-methyl-3-(pyrrolidin-1-yl)propan-2-olato]hexa­zinc(II) acetone disolvate, [Zn6Br4(C9H18NO)4(OH)4]·2C3H6O2, is generated by a crystallographic centre of symmetry. Two of the unique zinc atoms adopt distorted ZnO2NBr tetra­hedral coordination geometries and the other adopts a ZnO3N tetra­hedral arrangement. Both unique alkoxide ligands are N,O-chelating and both hydroxide ions are μ2 bridging. The crystal structure displays an O—H⋯O hydrogen bond between a μ2-OH group and an acetone solvent mol­ecule. The Hirshfeld surface has been calculated and is described.

The title compound, [FePt(C19H18OS2)(C18H15P)(C25H22P2)(CO)2],1, [(OC)2Fe(μ-dppm)(μ-C(=O)C(CH2SC6H4Me-4)=CCH2SC6H4Me-4)Pt(PPh3)], represents the first example of a diphosphane-bridged heterobimetallic Fe—Pt dimetallacyclopentenone complex resulting from a bimetallic activation of metal-coordinated carbonyl ligand with an internal alkyne, namely 1,4-bis(p-tolylthio)but-2-yne. The bridging μ2-C(=O)C(CH2SC6H4Me-4)=CCH2SC6H4Me-4 unit (stemming from a carbon–carbon coupling reaction between CO and the triple bond of the alkyne dithioether) forms a five-membered dimetallacyclopentenone ring, in which the C=C bond is π-coordinated to the Fe center. The latter is connected to the Pt center through a short metal–metal bond of 2.5697 (6) Å.

The title compound C

An efficient diastereoselective route is developed to get access to novel spiropyrrolo[1,2

The incorporation of heavy alkali metals into substrates is both challenging and essential for many reactions. Here, we report the formation of THF-solvated alkali metal benzyl compounds [PhCH2M ��� (thf)n] (M=Na, Rb, Cs). The synthesis was carried out by deprotonation of toluene with the bimetallic mixture n-butyllithium/alkali metal tert-butoxide and selective crystallization from THF of the defined benzyl compounds. Insights into the molecular structure in the solid as well as in solution state are gained by single crystal X-ray experiments and NMR spectroscopic studies. The compounds could be successfully used as alkali metal mediating reagents. The example of caesium showed the convenient use by deprotonating acidic C���H as well as N���H compounds to gain insight into the aminometalation using these reagents., Chemistry - a European journal;27(71)

The title compound, [FePt(C12H12O)(C18H15P)(C25H22P2)(CO)2]·2C7H8·CH2Cl2or [(OC)2Fe(μ-dppm)(μ-C(=O)C(2,4,5-C6H2Me3)=CH)Pt(PPh3)], represents an example of a diphosphane-bridged heterobimetallic dimetallacyclopentenone complex resulting from a bimetallic activation of 1-ethynyl-2,4,5-trimethylbenzene and a metal-coordinated carbonyl ligand. The bridging μ2-C(=O)C(2,4,5-C6H2Me3)=CH unit (stemming from a carbon–carbon coupling reaction between CO and the terminal alkyne) forms a five-membered dimetallacyclopentenone ring, in which the C=C bond is π-coordinated to the Fe centre. The latter is connected to the Pt centre through a short metal–metal bond of 2.5770 (5) Å. In the crystal, the complex is solvated by one dichloromethane and two toluene molecules.

A transition-metal-free direct electrolytic C-H amination involving an electrochemically generated nitrenium ion intermediate has been developed. The electrosynthesis takes place in the absence of any organoiodine catalysts and is enabled by an in situ generated electrolyte. A novel, efficient intramolecular and intermolecular C-H amination has been demonstrated using a simple reaction setup.

The synthesis and structural investigation of two dimethylphenylsilyllithium adducts with coordinating nitrogen donors quinuclidine and 1,3,5-tri-tert-butylhexahydro-1,3,5-triazine (tbtac) are presented. The structures show a comparatively long Si−Li distance and one amongst the shortest in monomeric silyllithiums reported so far, respectively. The structural investigations shed light on the influence of the donating additive for the lithium center on the structure of silyllithium compounds., Z. anorg. allg. Chem.;647(9)

A transition‐metal‐free direct electrolytic C−H amination involving an electrochemically generated nitrenium ion intermediate has been developed. The electrosynthesis takes place in the absence of any organoiodine catalysts and is enabled by an in situ generated electrolyte. A novel, efficient intramolecular and intermolecular C−H amination has been demonstrated using a simple reaction setup., ‘Power'ful Aminations. A simple transition‐metal‐free direct electrolytic amination strategy has been developed. The transformation takes place in the absence of any electrocatalyst by using cheap and easily available graphite electrodes. The reaction allows for the synthesis of carbazole derivatives via intramolecular C−H amination and also cross‐coupling of (hetero)arenes and various N‐arylamides in an undivided cell set up. The usage of an acidic solvent was beneficial as it eliminated the requirement of additional supporting electrolytes for the electrolysis.

The phosphonothioamidates (EtO)2P(=O)C(=S)N(H)R (L1 R = Cy; L2 R = Bz) have been prepared by nucleophilic addition of K[(EtO)2P(=O)] to R–N = C=S and crystallographically analyzed. Both compounds are associated pairwise through strong intermolecular N–H···O bonding giving rise to 10-membered supramolecular macrocycles. This intermolecular bonding has also been studied by Hirshfeld analysis of L1 and L2. Complexation of L on CuI in MeCN solution affords the dinuclear rhomboid-shaped thione complexes [{Cu(μ2-I)2Cu}(η1-L)2] (1a,b). Crystallographic characterization of 1a reveals that L1 is ligated exclusively via the thione function to the trigonal Cu(I) centers, which are interconnected through a short Cu–Cu bond of 2.6207(4) Å. In the solid state, individual dimeric complexes are associated through intermolecular N–H···O bonding generating a supramolecular 1D ribbon. The dinuclear complexes [{XHg(μ2-X)2HgX}(η1-L)2] (2a X = Br, L = Cy; 2b X = Br, L = Bz; 2c X = I, L = Bz) were formed by stoichiometric addition of L to HgX2. The molecular structures of 2b and 2c have been elucidated by X-ray diffraction studies, which show that individual complexes are connected through intermolecular N–H···O bonding generating a supramolecular 1D ribbon. Treatment of L1 with two equivalents of HgBr2 produces the tetranuclear compound [Hg4Br8(κ1-L1)2] 3, whose unusual bromide-bridged architecture has been elucidated by X-ray crystallography.

International audience; The dinuclear complexes [Co2(CO)6{P(OAr)3}2] (1a, Ar = Ph; 1b, Ar = o-Tol) were prepared and reacted with PhC≡CH and PhC≡CPh to yield dimetallatetrahedranes [{(ArO)3P}(OC)2Co-Co(μ-RC≡CPh)(CO)2{P(OAr)3}] (3a, Ar = Ph, R = H; 3b, Ar = o-Tol, R = H; 3c, Ar = Ph, R = Ph; 3d, Ar = o-Tol, R = Ph). The main reaction of diphenylacetylene was accompanied by a side reaction, leading to the dissociation of a P(OAr)3 ligand for the formation of mono(phosphite) complexes [{(ArO)3P}(OC)2Co-Co(μ-PhC≡CPh)(CO)3] (2b, R = Ph; 2d, R = o-Tol). The crystal structures of 1b, 3a, and 3d were determined along with that of the mono(phosphite) complex [{(PhO)3P}(OC)2Co-Co(μ-PhC≡CPh)(CO)3] 2b.

International audience; In a sustained search for novel α-amylase inhibitors for the treatment of type 2 diabetes mellitus (T2DM), we report herein the synthesis of a series of nineteen novel rhodanine-fused spiro[pyrrolidine-2,3’-oxindoles]. They were obtained by one-pot three component [3+2] cycloaddition of stabilized azomethine ylides, generated in situ by condensation of glycine methyl ester and the cyclic ketones 1H-indole-2,3-dione (isatin), with (Z)-5-arylidine-2-thioxothiazolidin-4-ones. The highlight of this protocol is the efficient high-yield construction of structurally diverse rhodanine-fused spiro[pyrrolidine-2,3'-oxindoles] scaffolds, including four contiguous stereocenters, along with excellent regio- and diastereoselectivities. The stereochemistry of all compounds was confirmed by NMR and corroborated by an X-ray diffraction study performed on one derivative. All cycloadducts were evaluated in vitro for their α-amylase inhibitory activity and showed good α-amylase inhibition with IC50 values ranging between 1.49± 0.10 and 3.06± 0.17µM, with respect to the control drug acarbose (IC50= 1.56µM). Structural activity relationships (SARs) were also established for all synthesized compounds and the binding interactions of the most active spiropyrrolidine derivatives were modelled by means of molecular in silico docking studies. The most potent compounds 5g, 5k, 5s and 5l were further screened in vivo for their hypoglycemic activity in alloxan-induced diabetic rats, showing a reduction of the blood glucose level. Therefore, these spiropyrrolidine derivatives may be considered as promising candidates for the development of new classes of antidiabetic drugs.

From the leaves of South African medicinal plant Melianthus comosus, four previously undescribed bufadienolides, 16β-formyloxymelianthugenin (1), 2β-acetoxymelianthusigenin (2), 2β-hydroxy-3β,5β-di-O-acetylhellebrigenin (3), and 2β-acetoxy-5β-O-acetylhellebrigenin (4) were isolated together with two known bufadienolides. The structural elucidation of the compounds was based on 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and other spectroscopic methods. The relative configurations were determined by single-crystal X-ray crystallography analysis and NOESY correlations. The isolated compounds displayed strong cytotoxicity against MCF-7 breast cancer cells, sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. Compound 1 showed the most potent activity, with IC50 values of 0.07 μM towards CCRF-CEM, 0.06 μM towards CEM/ADR5000 and 0.36 μM towards MCF-7 followed by compound 4 with IC50 values of 0.13 μM towards CCRF-CEM, 0.08 μM towards CEM/ADR5000 and 0.53 μM towards MCF-7.

The title compound, trimeth­yl(tetra­hydro­furan-κO)aluminium(III), is an addition product of tri­methyl­aluminium and tetra­hydro­furan (THF). Instead of a dimeric structure, which is very common for these types of compounds, a monomeric mol­ecular structure is observed., The title compound, trimeth­yl(tetra­hydro­furan-κO)aluminium(III), [Al(CH3)3(C4H8O)], is an addition product of tri­methyl­aluminium and tetra­hydro­furan (THF). Instead of a dimeric structure, which is very common for these types of compounds, a monomeric mol­ecular structure is observed. The C—Al—C angles in the mol­ecule are very different from the C—Al—C angles found in dimeric mol­ecular structures, leading to a different symmetry around the AlIII atom. The reasons for these differences are discussed.