Azotides as Modular Peptide-Based Ligands for Asymmetric Lewis Acid Catalysis

Synthesis of azotides and evaluation of these as ligands for enantioselective Lewis acid catalysis is reported. The ligands were readily prepared from the chiral pool of amino acids and perform well in the cobalt­(II)-catalyzed formation of asymmetric hetero Diels–Alder adducts. A rational for the observed enantioselectivity and conversion rate supported by computational calculations is provided

Stable gold(III) catalysts by oxidative addition of a carbon-carbon bond

Low-valent late transition-metal catalysis has become indispensable to chemical synthesis, but homogeneous high-valent transition-metal catalysis is underdeveloped, mainly owing to the reactivity of high-valent transition-metal complexes and the challenges associated with synthesizing them. Here we report a carbon-carbon bond cleavage at ambient conditions by a Au(I) complex that generates a stable Au(III) cationic complex. In contrast to the well-established soft and carbophilic Au(I) catalyst, this Au(III) complex exhibits hard, oxophilic Lewis acidity. For example, we observed catalytic activation of a,b-unsaturated aldehydes towards selective conjugate additions as well as activation of an unsaturated aldehyde-allene for a [2 1 2] cycloaddition reaction. The origin of the regioselectivity and catalytic activity was elucidated by X-ray crystallographic analysis of an isolated Au(III)-activated cinnamaldehyde intermediate. The concepts revealed suggest a strategy for accessing high-valent transition-metal catalysis from readily available precursors

1,4-Naphthoquinones in H‑Bond-Directed Trienamine-Mediated Strategies

The synthesis of optically active, carboannulated dihydronaphthoquinone and naphthoquinone derivatives with up to four stereogenic centers is demonstrated by H-bond-directed, trienamine-mediated [4 + 2]-cycloadditions. The outcome of the reaction between 2,4-dienals and 1,4-naphthoquinones is controlled by the substituent in the 2-position of the 1,4-naphthoquinone. In the case of sterically demanding 2-substituted derivatives, dihydronaphthoquinones are obtained. However, when a hydrogen atom is present in the 2-position, a subsequent oxidation of the initially formed cycloadducts occurs yielding naphthoquinones

Étienne-Hyacinthe de Ratte and Pierre Marie Auguste Broussonet, Montpellier, [France], to James Edward Smith, 12 Great Marlborough Street, London

De Ratte, secretary of the Académie des Sciences of Montpellier, informs Smith he has been elected a Correspondent Member. Broussonet has appended his own communication

Additional information on “Direct comparison of the in vitro and in vivo stability of DFO, DFO* and DFOcyclo* for 89Zr-immunoPET”

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Stable gold(III) catalysts by oxidative addition of a carbon–carbon bond

Whereas low-valent late transition metal catalysis has become indispensible for chemical synthesis, homogeneous high-valent transition metal catalysis is underdeveloped, mainly due to the reactivity of high-valent transition metal complexes and the challenges associated with synthesizing them. In this manuscript, we report a mild carbon-carbon bond cleavage reaction by a Au(I) complex that generates a stable Au(III) cationic complex. Complementary to the well-established soft and carbophilic Au(I) catalyst, this Au(III) complex exhibits hard, oxophilic Lewis acidity. This is exemplified by catalytic activation of α,β-unsaturated aldehydes towards selective conjugate additions as well as activation of an unsaturated aldehyde-allene for a [2 + 2] cycloaddition reaction. The origin of the regioselectivity and catalytic activity was elucidated by X-ray crystallographic analysis of an isolated Au(III)-activated cinnamaldehyde intermediate. The concepts revealed in this study provide a strategy for accessing high-valent transition metal catalysis from readily available precursors. Transition metal catalysis has been developed into an efficient and selective strategy for organic transformations in modern chemistry. Low-valent late transition metal complexe