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Experimental and computational analyses provide support for the existence of a metal-hydride-based mechanism for the ruthenium-mediated racemization of chiral alcohols.

Ethynylbenziodoxol(on)es (EBXs) have been widely used in organic synthesis as electrophilic alkyne-transfer reagents involving carbon- and heteroatom-based nucleophiles. However, potential reactions of EBXs with phenols remain uninvestigated. Here, we present the formation of (Z)-2-iodovinyl phenyl ethers with excellent regio- and stereoselectivity through the reactivity between EBXs and phenols driven by visible light. We propose that this light-activated transformation proceeds through electron donor-acceptor complexes to enable new reactivity beyond existing mechanisms for alkynylation of carbon- and heteroatom-based nucleophiles. This operationally robust process was employed for the synthesis of diverse (Z)-2-iodovinyl phenyl ethers through irradiating a solution containing a phenyl-EBX, a phenol, and the base Cs2CO3 with a commercially available blue LED at room temperature. The (Z)-2-iodovinyl phenyl ether products can be further stereospecifically functionalized to form trisubstituted alkenes, demonstrating the potential of these products en route to chemical complexity.

[11C]Carbon monoxide has been used in the palladium-mediated synthesis of [carbonyl-11C]ketones. Methyl iodide, vinylic and arylic halides and trifluoromethanesulfonates (triflates) have been coupled with tin reagents with insertion of [11C]carbon monoxide at very low concentrations (10-100 nmol[11C]CO in a total volume of 10 ml). The labelled products are obtained in 36-62% isolated decay-corrected radiochemical yields within 30 min of the end of radionuclide production. In order to use [11C]carbon monoxide efficiently, a gas handling system has been developed which allows the radioactive gas to recirculate through the reaction media. The reactions are performed using a one pot procedure. The best results are achieved with mixed tin reagents containing an unsaturated transferable substituent and Pd(AsPh3)4. In a typical experiment starting from 25 GBq of [11C]carbon dioxide, 4.2 GBq (47%) of [carbonyl-11C]acetophenone 1 is obtained 30 min after the end of radionuclide production. The specific radioactivity of 1 is 91 GBq μmol-1. [carbonyl-13C]Benzophenone 6 has been synthesised using the same approach to verify the position of the label.

The advent of saturated N-heterocycles as valuable building blocks in medicinal chemistry has led to the development of new methods to construct such nitrogen-containing cyclic frameworks. Despite the apparent strategic clarity, intramolecular C-H aminations with metallonitrenes have only sporadically been explored in this direction because of the intractability of the requisite alkyl nitrenes. Here, we report copper-catalysed intramolecular amination using an alkyl nitrene generated from substituted isoxazolidin-5-ones upon N-O bond cleavage. The copper catalysis exclusively aminates aromatic C(sp2)-H bonds among other potentially reactive groups, offering a solution to the chemoselectivity problem that has been troublesome with rhodium catalysis. A combined experimental and computational study suggested that the active species in the current cyclic β-amino acid synthesis is a dicopper alkyl nitrene, which follows a cyclisation pathway distinct from the analogous alkyl metallonitrene.

Acid-catalyzed methanolysis of N-hydroxy-α-oxobenzeneethanimidoyl chloride (1), a 2-(hydroxyimino)-1-phenylethan-1-one derivative obtained in one step from acetophenone, leads to a constant ratio of methyl α- oxobenzeneacetate (2) and methyl α-(hydroxyimino)benzeneacetate (3). 13C(α) Labelled [13C]-1 affords 13C(α) labelled [13C]-3, thus discarding the hypothesis of its formation via 1,2-arene migration. The reported sequence opens a novel approach to phenylglyoxylic and mandelic acid esters (=α-oxobenzeneacetic and α-hydroxybenzeneacetic acid esters), from acetophenone. The molecular structures of 1 and 3 were determined by X-ray structure analysis and compared with previously reported crystallographic data of α-oxo-oximes (=α-(hydroxyimino) ketones) 4 and 6-8. The unique stereoelectronic characteristics of the α-oxo-oxime moiety are discussed. All α-oxo-oximes share the following structural characteristics: (E)- configuration of the oxime C=N-OH bond (i.e. OH and C=O trans), the s-trans conformation of the oxo and imino moieties about the C(α)-C(=NOH) single bond, and intermolecular H-bonding. They differ from the isostructural α- diketone enols by the absence of resonance-assisted intramolecular H-bonding.

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A new electrochemical decarboxylative [4+2] annulation of arylglyoxylic acids with internal alkynes involving C-H functionalization by means of a cooperative anode and ruthenium catalysis is presented. This reaction represents a mechanistically novel strategy as an ideal supplement to the decarboxylative [4+2] annulation methodology by employing an electrooxidative process to avoid the use of an additional external oxidizing reagent and utilizing H2O as the carboxyl oxygen atom source to be engaged in the synthesis of 1H-isochromen-1-ones.

A palladium(II) catalyst promotes condensation of an N-aryl imine and an alkynylbenziodoxolone derivative to afford a multisubstituted furan, whose substituents are derived from the alkynyl moiety (2-position), the imine (3- and 4-positions), and the 2-iodobenzoate moiety (5-position), along with an N-arylformamide under mild conditions. The 2-iodophenyl group of the furan product serves as a versatile handle for further transformations. A series of isotope-labeling experiments shed light on the bond reorganization process in this unusual condensation reaction, which includes cleavage of the C-C triple bond and fragmentation of the carboxylate moiety.

An unexpected three-component iron-catalyzed reaction, comprising C-C bond cleavages in two components together with three times the cyclopropane formation and ring opening, is developed. The current reaction provides an unprecedented and efficient approa

(Chemical Equation Presented) There is substantial isomerization (k iso = 0.32 x 10-3 s-1) of 3-NO 2C6H413CH(Me)OS(18O) 2ToS during solvolysis (ksolv/

Crossover experiments between isotopomeric species of 2-diazo-1-oxo-1-phenylethane (18O, 13C, D) establish beyond doubt that the oxygen migration accompanying the photochemical Wolff rearrangement is not the result of intermolecular