61873-80-1Relevant academic research and scientific papers
Pd-Catalyzed ipso, meta-Dimethylation of ortho-Substituted Iodoarenes via a Base-Controlled C-H Activation Cascade with Dimethyl Carbonate as the Methyl Source
Wu, Zhuo,Wei, Feng,Wan, Bin,Zhang, Yanghui
, p. 4524 - 4530 (2021/05/04)
A methyl group can have a profound impact on the pharmacological properties of organic molecules. Hence, developing methylation methods and methylating reagents is essential in medicinal chemistry. We report a palladium-catalyzed dimethylation reaction of ortho-substituted iodoarenes using dimethyl carbonate as a methyl source. In the presence of K2CO3 as a base, iodoarenes are dimethylated at the ipso- and meta-positions of the iodo group, which represents a novel strategy for meta-C-H methylation. With KOAc as the base, subsequent oxidative C(sp3)-H/C(sp3)-H coupling occurs; in this case, the overall transformation achieves triple C-H activation to form three new C-C bonds. These reactions allow expedient access to 2,6-dimethylated phenols, 2,3-dihydrobenzofurans, and indanes, which are ubiquitous structural motifs and essential synthetic intermediates of biologically and pharmacologically active compounds.
Exhaustive Reduction of Esters Enabled by Nickel Catalysis
Cook, Adam,Prakash, Sekar,Zheng, Yan-Long,Newman, Stephen G.
supporting information, p. 8109 - 8115 (2020/05/20)
We report a one-step procedure to directly reduce unactivated aryl esters into their corresponding tolyl derivatives. This is achieved by an organosilane-mediated ester hydrosilylation reaction and subsequent Ni/NHC-catalyzed hydrogenolysis. The resulting conditions provide a direct and efficient alternative to multi-step procedures for this transformation that often require the use of hazardous metal hydrides. Applications in the synthesis of -CD3-containing products, derivatization of bioactive molecules, and chemoselective reduction in the presence of other C-O bonds are demonstrated.
C-H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C-P Functionalization
Mangin, Lo?c P.,Zargarian, Davit
, p. 4687 - 4700 (2019/12/24)
This report describes the results of a study on the C-H nickelation of phosphinites derived from variously substituted 1- and 2-naphthols, as well as the C-P functionalization of the Ni-naphthyl moiety arising from the C-H cyclonickelation. Refluxing 4-X-1-naphthyl phosphinites (X = H, 1a; MeO, 1b; Cl, 1c) with {(i-PrCN)NiBr2}n and Et3N in acetonitrile gave the nickelacyclic complexes {(κP,κC-4-X-1-OP(i-Pr)2-naphth-2-yl)Ni(μ-Br)}2, 2a-c, resulting from cyclonickelation at the C2-H, whereas cyclonickelation of the 2-naphthyl phosphinite analogue 1e under the same conditions occurred at C3-H. Placing a Me substituent at the C3 position of a 2-naphthyl phosphinite (1f) led to a very sluggish nickelation at the C1-H position, whereas 2-ethyl-1-naphthyl phosphinite (1d) failed to nickelate at C8-H. H/D scrambling tests conducted on the deuterated analogue of 1a (1a-d7) confirmed that nickelation occurs exclusively at C2. Similar tests conducted on deuterated analogues of alkyl-substituted 1- and 2-naphthyl phosphinites showed that no nickelation takes place at Csp3-H sites of the alkyl substituents. In contrast, very facile C-H nickelation was observed with 2-allyl-1-naphthyl phosphinite 1g to give a product featuring a π-allyl-Ni moiety. A series of tests have shown that the nickelation of substrates 1a, 1e, and 1f can be accelerated dramatically at 120-160 °C. On the other hand, conducting the high temperature reaction of 1a in the absence of Et3N resulted in an unanticipated and interesting C-P functionalization of the C2-H site, thus generating a i-Pr2P-substituted bidentate phosphine-phosphinite. A similar tandem C-H nickelation/C-P(O) functionalization was also observed at the C8-H position of substrate 1d. The mechanisms of these functionalization reactions have been probed and outlined.
A mild and ligand-free Ni-catalyzed silylation via C-OMe cleavage
Zarate, Cayetana,Nakajima, Masaki,Martin, Ruben
supporting information, p. 1191 - 1197 (2017/05/16)
Metal-catalyzed transformations that forge carbon-heteroatom bonds are of central importance in organic synthesis. Despite the formidable potential of aryl methyl ethers as coupling partners, the scarcity of metal-catalyzed C-heteroatom bond formations via C-OMe cleavage is striking, with isolated precedents requiring specialized, yet expensive, ligands, high temperatures, and π-extended backbones. We report an unprecedented catalytic ipso-silylation of aryl methyl ethers under mild conditions and without recourse to external ligands. The method is distinguished by its wide scope, which includes the use of benzyl methyl ethers, vinyl methyl ethers, and unbiased anisóle derivatives, thus representing a significant step forward for designing new C-heteroatom bond formations via C-OMe scission. Applications of this transformation in orthogonal silylation techniques as well as in further derivatizations are also described. Preliminary mechanistic experiments suggest the intermediacy of Ni(0)-ate complexes, leaving some doubt that a canonical catalytic cycle consisting of an initial oxidative addition of the C-OMe bond to Ni(0) species comes into play.
Ligand-free Ni-catalyzed reductive cleavage of inert carbon - Sulfur bonds
Barbero, Nekane,Martin, Ruben
, p. 796 - 799 (2012/04/23)
A catalytic reductive cleavage of C(sp2) - and C(sp3) - SMe bonds under ligandless conditions is presented. The method is characterized by its wide scope and high chemoselectivity profile including challenging substrate combinations, allowing the design of orthogonal and site-selectivity approaches.
Synthesis and structural analysis of oligo(naphthalene-2,3-diyl)s
Motomura, Takahisa,Nakamura, Hideko,Suginome, Michinori,Murakami, Masahiro,Ito, Yoshihiko
, p. 142 - 146 (2007/10/03)
Oligo(naphthalene-2,3-diyl)s are synthesized by the palladium-catalyzed cross-coupling reactions of 2-naphthyl-zinc compounds with 2-bromonaphthalene derivatives. An NMR analysis together with an X-ray diffraction study supports the conjecture that the helical secondary structure is a common feature of the assemblies in which naphthalene-like aromatic units are linked together between the β-positions in series.
Photochemistry of Stilbenes. 8. Eliminative Photocyclization of o-Methoxystilbenes
Mallory, Frank B.,Rudolph, M. Jonathan,Oh, Soon M.
, p. 4619 - 4626 (2007/10/02)
The synthetic value of the eliminative photocyclization of o-methoxystilbenes to give phenanthrenes with loss of the element of methanol has been enhanced by the use of tert-butyl alcohol as the solvent and sulfuric acid as a catalyst. 2-Methoxy-5-X-stilbenes and 2-methoxy-3-X-stilbenes undergo this photoreaction to produce the corresponding 2-X-phenanthrenes and 4-X-phenanthrenes, respectively.This regioselective photochemical route to these particular types of substituted phenanthrenes represents an improvement synthetically over the well-known oxidative photocyclization method with meta-substituted stilbenes, from which approximately 1:1 mixtures of 2-substituted and 4-substituted phenanthrenes usually are obtained.An attempt to extend the scope of this eliminative photocyclization method to the synthesis of benzanthracene by the ultraviolet irradiation of 3-methoxy-2-styrylnaphthalene was not successful, but this synthetic objective was achieved in an alternative way by the eliminative photocyclization of 5,6,7,8-tetrahydro-3-methoxy-2-styrylnaphthalene followed by oxidation of the resulting 8,9,10,11-tetrahydrobenzanthracene with DDQ.
