70 research outputs found
Chemodivergent Manganese-Catalyzed C–H Activation: Modular Synthesis of Fluorogenic Probes
Bioorthogonal diversification of peptides is generally dependent on impractical prefunctionalization methods. Here, the authors develop a manganese(I)-catalyzed C–H fluorescent labeling with BODIPY probes, which enables the development of activatable fluorophores to image cell function
Mild and Regioselective Pd(OAc)<sub>2</sub>‑Catalyzed C–H Arylation of Tryptophans by [ArN<sub>2</sub>]X, Promoted by Tosic Acid
A regioselective
Pd-mediated C–H bond arylation methodology
for tryptophans, utilizing stable aryldiazonium salts, affords C2-arylated
tryptophan derivatives, in several cases quantitatively. The reactions
proceed in air, without base, and at room temperature in EtOAc. The
synthetic methodology has been evaluated and compared against other
tryptophan derivative arylation methods using the CHEM21 green chemistry
toolkit. The behavior of the Pd catalyst species has been probed in
preliminary mechanistic studies, which indicate that the reaction
is operating homogeneously, although Pd nanoparticles are formed during
substrate turnover. The effects of these higher order Pd species on
catalysis, under the reaction conditions examined, appear to be minimal:
e.g., acting as a Pd reservoir in the latter stages of substrate turnover
or as a moribund form (derived from catalyst deactivation). We have
determined that TsOH shortens the induction period observed when [ArN<sub>2</sub>]BF<sub>4</sub> salts are employed with Pd(OAc)<sub>2</sub>. Pd(OTs)<sub>2</sub>(MeCN)<sub>2</sub> was found to be a superior
precatalyst (confirmed by kinetic studies) in comparison to Pd(OAc)<sub>2</sub>
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