A palladium-catalyzed ortho-alkoxylation of anilides with both primary and secondary alcohols via ligand-directed C-H activation has been explored. This alkoxylation promoted by catalytic ...methanesulfonic acid proceeds well at room temperature in most cases and affords aryl alkyl ethers in moderate to good yields.
Hydrosilylation of unsaturated carbon-carbon bonds with hydrosilanes is a very important process to access organosilicon compounds and ranks as one of the most fundamental reactions in organic ...chemistry. However, catalytic asymmetric hydrosilylation of activated alkenes and internal alkenes has proven elusive, due to competing reduction of carbon-carbon double bond or isomerization processes. Herein, we report a highly enantioselective Si-C coupling by hydrosilylation of carbonyl-activated alkenes using a palladium catalyst with a chiral TADDOL-derived phosphoramidite ligand, which inhibits O-hydrosilylation/olefin reduction. The stereospecific Si-C coupling/hydrosilylation of maleimides affords a series of silyl succinimides with up to 99% yield, >99:1 diastereoselectivity and >99:1 enantioselectivity. The high degree of stereoselectivity exerts remote control of axial chirality, leading to functionalized, axially chiral succinimides which are versatile building blocks. The product utility is highlighted by the enantioselective construction of N-heterocycles bearing up to three stereocenters.
A highly efficient electrochemical reduction of 60fullerene-fused lactones to 60fullerene-fused ketones, a formal process of retro Baeyer-Villiger reaction, has been achieved for the first time. The ...electrochemically generated dianionic 60fullerene-fused lactones can be transformed into 60fullerene-fused ketones in the presence of acetic acid in 85-91% yields. Control experiments have been performed to elucidate the reaction mechanism. The products have been characterized with spectroscopic data and single-crystal X-ray analysis. Moreover, the electrochemical properties have also been investigated.
Herein, we report divergent additions of 2,2′‐diazidobiphenyls to C60 and Sc3N@Ih‐C80. In stark contrast to that of the previously reported bis‐azide additions, the unexpected cascade reaction leads ...to the dearomative formation of azafulleroids 2 fused with a 7‐6‐5‐membered ring system in the case of C60. In contrast, the corresponding reaction with Sc3N@Ih‐C80 switches to the C−H insertion pathway, thereby resulting in multiple isomers, including a carbazole‐derived 6,6‐azametallofulleroid 3 and a 5,6‐azametallofulleroid 4 and an unusual 1,2,3,6‐tetrahydropyrrolo3,2‐ccarbazole‐derived metallofullerene 5, whose molecular structures have been unambiguously determined by single‐crystal X‐ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole‐derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the 5,6‐isomer 4 to the 5,6‐isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between 5,6‐ and 6,6‐isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.
Divergent reactivities of 2,2′‐diazidobiphenyls toward C60 and Sc3N@Ih‐C80 have been disclosed. In the case of C60, a dearomative cascade reaction results in the formation of azafulleroids fused with a 7‐6‐5‐membered ring system, whereas Sc3N@Ih‐C80 undergoes a C−H insertion pathway, with the generation of carbazole‐derived 6,6‐ and 5,6‐azametallofulleroids and an unusual 1,2,3,6‐tetrahydropyrrolo3,2‐ccarbazole‐derived metallofullerene.
Endohedral clusterfullerenes exhibit unique chemical properties due to intramolecular electron transfer of the encaged metal cluster to the outer fullerene cages. We report the synthesis of two ...Sc3N@D3h‐C78 monoadducts 2 a and 2 b through the 1,3‐dipolar reaction of Sc3N@D3h‐C78 with carbonyl ylide bearing anomalous cis‐conformation regioselectivity. The molecular structures of these monoadducts are unambiguously confirmed by single‐crystal X‐ray crystallography, revealing that both 2 a and 2 b have cis‐conformations with the furan moiety grafted via 6,6‐closed addition patterns. Under the same conditions, the control reaction of C60 with carbonyl ylide affords two monoadducts 3 a and 3 b, which exhibit cis‐ and trans‐conformations, respectively, with 6,6‐closed addition patterns. According to theoretical calculations, the exclusive formation of the cis‐only Sc3N@D3h‐C78 monoadducts is a consequence of conjunct effects of thermodynamic stability of adducts, the reactivity of the addition site, and the cis‐dipole intermediate from trans 1.
Sc3N@D3h‐C78 was reacted with carbonyl ylide to form two isomeric monoadducts 2 a and 2 b bearing anomalous cis‐conformation regioselectivity and a 6,6‐closed addition pattern. Whereas isomeric monoadducts 3 a and 3 b with cis‐ and trans‐conformations were produced simultaneously for C60 under the same conditions. Adduct stability, reactivity of the addition site, and the nature of intermediates play a role in the different regioselectivity.
The direct decarboxylative meta-selective C–H acylation of a wide range of arenes is established via the ruthenium-catalyzed ortho-metalation strategy. This procedure, using Ru3(CO)12 as the catalyst ...and α-oxocarboxylic acids as the acylation source, featured broad substrate scope, good functional group tolerance, and high regioselectivity. Mechanistic studies demonstrated that a radical process and an 18e-octahedral ruthenium species were involved in this reaction. The present work provides a new strategy for the regioselective meta-acylation reactions and will be a powerful tool for the development of pharmaceutical and materials science.
The solvent-free mechanochemical reaction has aroused increasing interest among scientists. Mechanical ball-milling can implement reactions under mild conditions, shorten the reaction time, and ...improve the reaction efficiency. Particularly, the most attractive characteristic of mechanochemistry is that it can alter the reaction pathway. However, few such examples have been reported so far. In this paper, we report the reaction of aldoximes with NaCl and Oxone under ball-milling conditions to afford
-acyloxyimidoyl chlorides, which are different from those of the liquid-phase counterpart.
Unprecedented chiral multilayer folding 3D polymers have been assembled and regulated by uniform and differentiated aromatic chromophore units between naphthyl piers. Screening catalysts, catalytic ...systems and monomers were proven to be crucial for asymmetric catalytic Suzuki–Miyaura polycouplings for this assembly. X‐ray crystallography of the corresponding dimers and trimers revealed the absolute configuration and the intermolecular packing pattern. Up to 61 960 Mw/41 900 Mn and m/z 4317 for polymers and oligomers, as confirmed by gel permeation chromatography (GPC) and MALDI‐TOF MS, indicated that these frameworks were composed of multiple stacked layers. The resulting multiple π‐assemblies exhibited remarkable optical properties in aggregated states (photoluminescence in solids and aggregation‐induced emission in solutions), as well as reversible redox properties in electrochemical performance.
A first asymmetric catalytic approach to multilayer 3D folding polymers by using Suzuki–Miyaura cross‐coupling in the presence of chiral catalysts. The resulting multiple π‐assemblies exhibited remarkable optical properties in aggregated states (photoluminescence in solids and aggregation‐induced emission in solutions), as well as reversible redox properties in electrochemical performance.
An efficient protocol has been developed for the desulfitative Heck‐type reaction of aryl sulfinic acids with a variety of alkenes in the presence of a catalytic amount of Pd(OAc)2 and inexpensive ...Cu(OAc)2 as oxidant. This method does not require a ligand or a base, thereby broadening the scope of Pd‐catalyzed coupling reactions.
PDF
