Oxidative single-electron transfer-catalyzed tandem reactions consisting of a conjugate addition and a radical cyclization are reported, which incorporate the mandatory terminal oxidant as a functionality into the product.
anti‐β‐Amino‐α‐(aminoxy) esters or amides are synthesized by merging polar asymmetric aza‐Michael additions of lithium 1‐phenylethylamides to α,β‐unsaturated carboxylic acid derivatives and diastereoselective radical couplings with the persistent free radical TEMPO mediated or catalyzed by ferrocenium hexafluorophosphate. Aliphatic α,β‐unsaturated carboxylic derivatives gave good to excellent anti‐diastereoselectivity for the radical coupling step, whereas the selectivity remained lower for cinnamic acid derivatives. The method allows the convenient introduction of a protected oxygen functionality, which is stable to acidic, basic, hydride and hydrogenolytic reductive conditions, but can be deprotected with zinc and acetic acid in the presence of TBDMS and Boc groups without noticeable epimerization. The tandem aza‐Michael/oxygenation strategy was applied in total syntheses of the TH2 cytokine secretion modulator cytoxazone, and dipeptide fragments of the anti‐β‐amino‐α‐hydroxy acid containing macrocyclic peptides perthamide C and largamide H.
A simple two-step method for the selective preparation of anomerically pure 1α- and 1β-(indol-2-yl)deoxyribose derivatives was developed. The synthesis was based on the Sonogashira reaction of 1α- and 1β-ethynyldeoxyribose and 2-haloanilines followed by a Pd-complex catalyzed cyclization to the corresponding indolyldeoxyribosides.
In der richtigen Staffelung an Olefine: Vinylboronate ermöglichen die gestaffelte Addition nucleophiler und elektrophiler oder nucleophiler und Radikal‐erzeugender Kohlenstoffreagentien an die Doppelbindung unter Erhaltung der wertvollen Boronatgruppe. Schlüssel zum Erfolg dieser schwierigen Strategie zur zweifachen C‐C‐Kupplung sind die Verlagerung der nucleophilen Addition zum B‐Atom und eine 1,2‐Metallat‐Umlagerung, die den Substituenten danach zum C‐Atom überträgt.
Smooth handoff in the relay: Vinyl boronates enable the direct addition of nucleophilic and electrophilic or nucleophilic and radical-generating carbon reagents across the double bond with retention of the valuable boronate group. The key to the success of this difficult twofold C-C bond-formation strategy is the initial relay of the nucleophilic addition to boron and the rearrangement of a 1,2-metalate rearrangement, shuttling it to the carbon atom.
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