52806-22-1Relevant academic research and scientific papers
Solvent coordination to palladium can invert the selectivity of oxidative addition
Elias, Emily K.,Neufeldt, Sharon R.,Rehbein, Steven M.
, p. 1618 - 1628 (2022/02/21)
Reaction solvent was previously shown to influence the selectivity of Pd/PtBu3-catalyzed Suzuki-Miyaura cross-couplings of chloroaryl triflates. The role of solvents has been hypothesized to relate to their polarity, whereby polar solvents stabilize anionic transition states involving [Pd(PtBu3)(X)]- (X = anionic ligand) and nonpolar solvents do not. However, here we report detailed studies that reveal a more complicated mechanistic picture. In particular, these results suggest that the selectivity change observed in certain solvents is primarily due to solvent coordination to palladium. Polar coordinating and polar noncoordinating solvents lead to dramatically different selectivity. In coordinating solvents, preferential reaction at triflate is likely catalyzed by Pd(PtBu3)(solv), whereas noncoordinating solvents lead to reaction at chloride through monoligated Pd(PtBu3). The role of solvent coordination is supported by stoichiometric oxidative addition experiments, density functional theory (DFT) calculations, and catalytic cross-coupling studies. Additional results suggest that anionic [Pd(PtBu3)(X)]- is also relevant to triflate selectivity in certain scenarios, particularly when halide anions are available in high concentrations.
Gram-Scale Robust Synthesis of 1-Chloro-2,3-dimethyl-4-phenylnaphthalene: A Promising Scaffold with Three Contiguous Reaction Positions
Moriguchi, Kento,Kono, Taro,Seko, Shinzo,Tanabe, Yoo
, p. 3811 - 3817 (2020/10/21)
A three-step reaction sequence for the gram-scale synthesis of 1-chloro-2,3-dimethyl-4-phenylnaphthalene was developed. (i) Stereoselective dichlorocarbene addition to methyl angelate afforded methyl (1 S*,3 S*)-2,2-dichloro-1,3-dimethylcyclopropane-1-carboxylate (78% yield, >98% purity, distillation). (ii) Addition reaction of two molar amounts of PhLi afforded (1 S*,3 S*)-2,2-dichloro-1,3-dimethylcyclopropyldiphenylmethanol (81% yield, >98% purity, recrystallization). (iii) Key SnCl 4-mediated benzannulation produced the desired product (83% yield, >98% purity, recrystallization) with three contiguous reaction sites. Five derivatization examples including benzylic reactions and cross-couplings at the pendant Cl-position are demonstrated. Some relevant distinctive benzannulations are also discussed.
Small Phosphine Ligands Enable Selective Oxidative Addition of Ar-O over Ar-Cl Bonds at Nickel(0)
Entz, Emily D.,Hooker, Leidy V.,Neufeldt, Sharon R.,Russell, John E. A.
, p. 15454 - 15463 (2020/10/18)
Current methods for Suzuki-Miyaura couplings of nontriflate phenol derivatives are limited by their intolerance of halides including aryl chlorides. This is because Ni(0) and Pd(0) often undergo oxidative addition of organohalides at a similar or faster rate than most Ar-O bonds. DFT and stoichiometric oxidative addition studies demonstrate that small phosphines, in particular PMe3, are unique in promoting preferential reaction of Ni(0) with aryl tosylates and other C-O bonds in the presence of aryl chlorides. This selectivity was exploited in the first Ni-catalyzed C-O-selective Suzuki-Miyaura coupling of chlorinated phenol derivatives where the oxygen-containing leaving group is not a fluorinated sulfonate such as triflate. Computational studies suggest that the origin of divergent selectivity between PMe3 and other phosphines differs from prior examples of ligand-controlled chemodivergent cross-couplings. PMe3 effects selective reaction at tosylate due to both electronic and steric factors. A close interaction between nickel and a sulfonyl oxygen of tosylate during oxidative addition is critical to the observed selectivity.
Novel method for the synthesis of α- and β-halogenonaphthalenes by regioselective benzannulation of aryl(gem-dihalogenocyclopropyl)methanols: Application to the total synthesis of the lignan lactones, justicidin E and taiwanin C
Tanabe, Yoo,Seko, Shinzo,Nishii, Yoshinori,Yoshida, Taichi,Utsumi, Naoka,Suzukamo, Gohfu
, p. 2157 - 2165 (2007/10/03)
Acid treatment of two types of aryl(gem-dihalogenocyclopropyl)methanols (ADCMs) 1 and 3 gives α- and β-halogenonaphthalenes in good yields with excellent selectivity. These alternative annulations involve two distinctive types of highly regioselective acid-induced cyclopropane ring cleavage, wherein the preferential formation of more stable cationic intermediates determines the selectivity. The stereochemical mode of both the preparation and the annulation between diastereoisomers of an ADCM has been checked. As a demonstration of this annulation, a total synthesis of each of the natural lignan lactones, justicidin E 19 and taiwanin C 20, has also been performed. Since these 4-arylnaphthalenes are expected to exhibit biological activity, the anti-platelet activating factor (anti-PAF) activity of justicidin E has been assayed.
