A combination of visible light photocatalysis and gold catalysis is applied to a ring expansion–oxidative arylation reaction. The reaction provides an entry into functionalized cyclic ketones from ...the coupling reaction of alkenyl and allenyl cycloalkanols with aryl diazonium salts. A mechanism involving generation of an electrophilic gold(III)–aryl intermediate is proposed on the basis of mechanistic studies, including time-resolved FT-IR spectroscopy.
New modes of DODH: Oxorhenium compounds act as deoxydehydration(DODH)/acid dual‐purpose catalysts to transform biomass‐derived diol substrates into a variety of commodity chemical precursors. The ...power of this approach is highlighted by a tandem 1,3‐OH shift/DODH of 2‐ene‐1,4‐diols and 2,4‐diene‐1,6‐diols, and by a DODH/esterification sequence of sugar acids to unsaturated esters for the production of polymers and plasticizers.
Novel chiral iron phosphate complexes were prepared as catalysts for asymmetric oxidative coupling reactions. These catalysts were applied for the synthesis of enantio-enriched C 1- and C 2-symmetric ...BINOLs, in which the 3 and 3′ positions are available for chemical modifications. It was proposed that the reaction takes place via an oxidative radical-anion coupling mechanism. A destructive BINOL racemization that competes with the enantioselective oxidative coupling of 2-naphthols was revealed, thereby offering new insights into this highly important reaction.
Performing selective transformations on complex substrates remains a challenge in synthetic chemistry. These difficulties often arise due to cross-reactivity, particularly in the presence of similar ...functional groups at multiple sites. Therefore, there is a premium on the ability to perform selective activation of these functional groups. We report here a supramolecular strategy where encapsulation of a hydrogenation catalyst enables selective olefin hydrogenation, even in the presence of multiple sites of unsaturation. While the reaction requires at least one sterically nondemanding alkene substituent, the rate of hydrogenation is not sensitive to the distance between the alkene and the functional group, including a carboxylate, on the other substituent. This observation indicates that only the double bond has to be encapsulated to effect hydrogenation. Going further, we demonstrate that this supramolecular strategy can overcome the inherent allylic alcohol selectivity of the free catalyst, achieving supramolecular catalyst-directed regioselectivity as opposed to directing-group selectivity.
A new method for the P-arylation of aryldiazonium salts with H-phosphonates
dual gold and photoredox catalysis is described. The reaction proceeds smoothly at room temperature in the absence of base ...and/or additives, and offers an efficient approach to arylphosphonates. The reaction is proposed to proceed through a photoredox-promoted generation of an electrophilic arylgold(III) intermediate that undergoes coupling with the H-phosphonate nucleophile.
Despite the tremendous advances of the past four decades, chemists are far from being able to use chiral catalysts to control the stereoselectivity of any desired reaction. New concepts for the ...construction and mode of operation of chiral catalysts have the potential to open up previously inaccessible reaction space. The recognition and categorization of distinct approaches seems to play a role in triggering rapid exploration of new territory. This Review both reflects on the origins as well as details a selection of the latest examples of an area that has advanced considerably within the past five years or so: the use of chiral anions in asymmetric catalysis. Defining reactions as involving chiral anions is a difficult task owing to uncertainties over the exact catalytic mechanisms. Nevertheless, we attempt to provide an overview of the breadth of reactions that could reasonably fall under this umbrella.
Cysteine can be specifically functionalized by a myriad of acid-base conjugation strategies for applications ranging from probing protein function to antibody-drug conjugates and proteomics. In ...contrast, selective ligation to the other sulfur-containing amino acid, methionine, has been precluded by its intrinsically weaker nucleophilicity. Here, we report a strategy for chemoselective methionine bioconjugation through redox reactivity, using oxaziridine-based reagents to achieve highly selective, rapid, and robust methionine labeling under a range of biocompatible reaction conditions. We highlight the broad utility of this conjugation method to enable precise addition of payloads to proteins, synthesis of antibody-drug conjugates, and identification of hyperreactive methionine residues in whole proteomes.
Here we report the direct asymmetric amination of α-substituted cyclic ketones catalyzed by a chiral phosphoric acid, yielding products with a N-containing quaternary stereocenter in high yields and ...excellent enantioselectivities. Kinetic resolution of the starting ketone was also found to occur on some of the substrates under milder conditions, providing enantioenriched α-branched ketones, another important building block in organic synthesis. The utility of this methodology was demonstrated in the short synthesis of (S)-ketamine, the more active enantiomer of this versatile pharmaceutical.
A highly enantioselective dearomative Rautenstrauch rearrangement catalyzed by cationic (S)-DTBM-Segphosgold(I) is reported. This reaction provides a straightforward method to prepare ...enantioenriched cyclopentabindoles. These studies show vast difference in enantioselectivity in the reactions of propargyl acetates and propargyl acetals in the chiral ligand-controlled Rautenstrauch reaction.
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