RESUMO
Correction for 'Simple synthetic access to [Au(IBiox)Cl] complexes' by Ekaterina A. Martynova et al., Dalton Trans., 2023, 52, 7558-7563, https://doi.org/10.1039/D3DT01357J.
RESUMO
The divergent synthesis of two indane polyketides of the indidene family, namely (±)-indidene A (11 steps, 1.7 %) and (+)-indidene C (13 steps, 1.3 %), is reported. The synthesis of the trans-configured common indane intermediate was enabled by palladium(0)-catalyzed methylene C(sp3 )-H arylation, which was performed in both racemic and enantioselective (e.r. 99 : 1) modes. Further elaboration of this common intermediate by nickel-catalyzed dehydrogenative coupling allowed the rapid installation of the aroyl moiety of (±)-indidene A. In parallel, the biphenyl system of (±)- and (+)-indidene C was constructed by Suzuki-Miyaura coupling. These investigations led us to revise the structures of indidenes B and C.
RESUMO
We report mechanistic studies on the reactivity of different α-substituted C(sp3)-H bonds, -CHnR (R = H, Me, CO2Me, CONMe2, OMe, and Ph, as well as the cyclopropyl and isopropyl derivatives -CH(CH2)2 and -CHMe2) in the context of Pd0-catalyzed C(sp3)-H arylation. Primary kinetic isotope effects, kH/kD, were determined experimentally for R = H (3.2) and Me (3.5), and these, along with the determination of reaction orders and computational studies, indicate rate-limiting C-H activation for all substituents except when R = CO2Me. This last result was confirmed experimentally (kH/kD â¼ 1). A reactivity scale for C(sp3)-H activation was then determined: CH2CO2Me > CH(CH2)2 ≥ CH2CONMe2 > CH3 â« CH2Ph > CH2Me > CH2OMe â« CHMe2. C-H activation involves AMLA/CMD transition states featuring intramolecular O â H-C H-bonding assisted by C-H â Pd agostic bonding. The "AMLA coefficient", χ, is introduced to quantify the energies associated with these interactions via natural bond orbital 2nd order perturbation theory analysis. Higher barriers correlate with lower χ values, which in turn signal a greater agostic interaction in the transition state. We believe that this reactivity scale and the underlying factors that determine this will be of use for future studies in transition-metal-catalyzed C(sp3)-H activation proceeding via the AMLA/CMD mechanism.
RESUMO
Green and sustainable access to chiral and achiral gold-IBiox complexes is reported. The gold complexes were synthesized using a simple, air-tolerant, weak base protocol carried out in a green solvent. Their catalytic activity was examined in the hydroamination of alkynes. The steric protection afforded the gold center by these ligands was quantified using the %Vbur model and compared with the most commonly encountered NHCs.
RESUMO
The enantioselective functionalization of nonactivated enantiotopic secondary C-H bonds is one of the greatest challenges in transition-metal-catalyzed C-H activation proceeding by an inner-sphere mechanism. Such reactions have remained elusive within the realm of Pd0 catalysis. Reported here is the unique reactivity profile of the IBiox ligand family in the Pd0 -catalyzed intramolecular arylation of such nonactivated secondary C-H bonds. Chiral C2 -symmetric IBiox ligands led to high enantioselectivities for a broad range of valuable indane products containing a tertiary stereocenter, as well as the arylation of secondary C-H bonds adjacent to amides. Depending on the amide substituents and upon control of reaction time, indanes containing labile tertiary stereocenters were also obtained with high enantioselectivities. Analysis of the steric maps of the IBiox ligands indicated that the level of enantioselectivity correlates with the difference between the two most occupied and the two less occupied space quadrants, and provided a blueprint for the design of even more efficient ligands.
