21 research outputs found
α-Radical Phosphines: Synthesis, Structure, and Reactivity
A series of phosphines featuring a persistent radical were synthesized in two steps by condensation of dialkyl-/diarylchlorophosphines with stable cyclic (alkyl)(amino)carbenes (cAACs) followed by one-electron reduction of the corresponding cationic intermediates. Structural, spectroscopic, and computational data indicate that the spin density in these phosphines is mainly localized on the original carbene carbon from the cAAC fragment; thus, it remains in the α-position with respect to the central phosphorus atom. The potential of these α-radical phosphines to serve as spin-labeled ligands is demonstrated through the preparation of several AuI derivatives, which were also structurally characterized by single-crystal X-ray diffraction
Synthesis and reactivity of α-cationic phosphines: the effect of imidazolinium and amidinium substituents
Mono- and dicationic phosphines have been synthesized through the reaction of chloroimidazolinium or chloroamidinium salts with secondary or primary phosphines respectively. The resulting ligands, which depict a significantly reduced donor ability compared with their neutral analogues, have been used to design Pt(II) and Au(I) complexes that effectively catalyse the hydroarylation of alkynes
Strain radial y circunferencial como marcadores de fibrosis en un modelo experimental de infarto de miocardio
Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes
We
report copper-catalyzed oxidative dehydrogenative carboxylation
(ODC) of unactivated alkanes with various substituted benzoic acids
to produce the corresponding allylic esters. Spectroscopic studies
(EPR, UV–vis) revealed that the resting state of the catalyst
is [(BPI)Cu(O<sub>2</sub>CPh)] (<b>1-O</b><sub><b>2</b></sub><b>CPh</b>), formed from [(BPI)Cu(PPh<sub>3</sub>)<sub>2</sub>], oxidant, and benzoic acid. Catalytic and stoichiometric
reactions of <b>1-O</b><sub><b>2</b></sub><b>CPh</b> with alkyl radicals and radical probes imply that C–H bond
cleavage occurs by a <i>tert</i>-butoxy radical. In addition,
the deuterium kinetic isotope effect from reactions of cyclohexane
and <i>d</i><sub>12</sub>-cyclohexane in separate
vessels showed that the turnover-limiting step for the ODC of cyclohexane
is C–H bond cleavage. To understand the origin of the difference
in products formed from copper-catalyzed amidation and copper-catalyzed
ODC, reactions of an alkyl radical with a series of copper–carboxylate,
copper–amidate, and copper–imidate complexes were performed.
The results of competition experiments revealed that the relative
rate of reaction of alkyl radicals with the copper complexes follows
the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate.
Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates
containing more electron-rich aryl groups on the benzamidate and benzoate
react faster with the alkyl radical than do those with more electron-poor
aryl groups on these ligands to produce the corresponding products.
These data on the ODC of cyclohexane led to preliminary investigation
of copper-catalyzed oxidative dehydrogenative amination of cyclohexane
to generate a mixture of <i>N</i>-alkyl and <i>N</i>-allylic products