33942-00-6Relevant articles and documents
Efficient C-H Amination Catalysis Using Nickel-Dipyrrin Complexes
Betley, Theodore A.,Clarke, Ryan M.,Dong, Yuyang,Porter, Gerard J.
, p. 10996 - 11005 (2020/07/08)
A dipyrrin-supported nickel catalyst (AdFL)Ni(py) (AdFL: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine) displays productive intramolecular C-H bond amination to afford N-heterocyclic products using aliphatic azide substrates. The catalytic amination conditions are mild, requiring 0.1-2 mol% catalyst loading and operational at room temperature. The scope of C-H bond substrates was explored and benzylic, tertiary, secondary, and primary C-H bonds are successfully aminated. The amination chemoselectivity was examined using substrates featuring multiple activatable C-H bonds. Uniformly, the catalyst showcases high chemoselectivity favoring C-H bonds with lower bond dissociation energy as well as a wide range of functional group tolerance (e.g., ethers, halides, thioetheres, esters, etc.). Sequential cyclization of substrates with ester groups could be achieved, providing facile preparation of an indolizidine framework commonly found in a variety of alkaloids. The amination cyclization reaction mechanism was examined employing nuclear magnetic resonance (NMR) spectroscopy to determine the reaction kinetic profile. A large, primary intermolecular kinetic isotope effect (KIE = 31.9 ± 1.0) suggests H-atom abstraction (HAA) is the rate-determining step, indicative of H-atom tunneling being operative. The reaction rate has first order dependence in the catalyst and zeroth order in substrate, consistent with the resting state of the catalyst as the corresponding nickel iminyl radical. The presence of the nickel iminyl was determined by multinuclear NMR spectroscopy observed during catalysis. The activation parameters (ΔH? = 13.4 ± 0.5 kcal/mol; ΔS?= -24.3 ± 1.7 cal/mol·K) were measured using Eyring analysis, implying a highly ordered transition state during the HAA step. The proposed mechanism of rapid iminyl formation, rate-determining HAA, and subsequent radical recombination was corroborated by intramolecular isotope labeling experiments and theoretical calculations.
Preparation and characterization of magnetically separable MgFe2O4/Mg(OH)2 nanocomposite as an efficient heterogeneous catalyst for regioselective one-pot synthesis of β-chloroacetates from epoxides
Hassanzadeh, Shadi,Eisavi, Ronak,Abbasian, Mojtaba
, (2018/09/06)
Magnetically separable MgFe2O4/Mg(OH)2 nanoparticles were fabricated and characterized using various techniques. These nanoparticles were used as a new catalyst for regioselective one-pot synthesis of β-chloroacetates from epoxides in the presence of NiCl2?6H2O and acetic anhydride. All reactions were carried out in ethanol at room temperature within 22–80?min giving the β-chloroacetates in high to excellent yields. The nanocatalyst was easily separated using an external magnet and reused several times without any significant loss of efficiency or magnetic property.
Catalyst-free, direct, high regio- and chemoselective conversion of epoxides to vicinal haloesters under mild, neutral, and solvent-free conditions
Aghapour, Ghasem,Hatefipour, Razieh
, p. 1030 - 1040 (2013/03/14)
A catalyst-free, high regio- and chemoselective method is described for the mild conversion of wide varieties of epoxides directly to their corresponding vicinal haloesters using quaternary ammonium halides R4N +X- (X equa
Silver-catalyzed decarboxylative chlorination of aliphatic carboxylic acids
Wang, Zhentao,Zhu, Lin,Yin, Feng,Su, Zhongquan,Li, Zhaodong,Li, Chaozhong
experimental part, p. 4258 - 4263 (2012/04/10)
Decarboxylative halogenation of carboxylic acids, the Hunsdiecker reaction, is one of the fundamental functional group transformations in organic chemistry. As the initial method requires the preparations of strictly anhydrous silver carboxylates, several modifications have been developed to simplify the procedures. However, these methods suffer from the use of highly toxic reagents, harsh reaction conditions, or limited scope of application. In addition, none is catalytic for aliphatic carboxylic acids. In this Article, we report the first catalytic Hunsdiecker reaction of aliphatic carboxylic acids. Thus, with the catalysis of Ag(Phen)2OTf, the reactions of carboxylic acids with t-butyl hypochlorite afforded the corresponding chlorodecarboxylation products in high yields under mild conditions. This method is not only efficient and general, but also chemoselective. Moreover, it exhibits remarkable functional group compatibility, making it of more practical value in organic synthesis. The mechanism of single electron transfer followed by chlorine atom transfer is proposed for the catalytic chlorodecarboxylation.
Convenient synthesis of chlorohydrins from epoxides using zinc oxide: Application to 5,6-epoxysitosterol
Moghaddam, Firouz Matloubi,Saeidian, Hamdollah,Mirjafary, Zohreh,Javan, Marjan Jebeli,Farimani, Mehdi Moridi,Seirafi, Marjan
experimental part, p. 157 - 163 (2009/09/30)
Efficient synthesis of protected and unprotected chlorohydrins has been achieved by ring opening of epoxides with acetyl/benzoyl chloride and TMSCl using a catalytic amount of ZnO as a reusable catalyst. The applicability of ZnO is further extended by performing the cleavage of the natural product 5,6-epoxysitosterol with acetyl chloride.
Organomercury/aluminum-mediated acylative cleavage of cyclic ethers
Luzzio, Frederick A.,Bobb, Rhiana A.
, p. 1851 - 1858 (2007/10/03)
Epoxides and tetrahydrofurans are cleaved with concomitant acylation to chloroalkyl esters using a reagent system composed of an organomercurial, aluminum metal and an acid chloride. The cleavage is promoted under mild conditions by a range of readily-available cyclic β-alkoxychloromercurials and acid chlorides. Using mainly tetrahydrofuran and cyclohexene oxide as substrates, the yield of isolated chloroesters ranged from 52 to 96%.
Efficient and Regioselective Conversion of Epoxides into Vicinal Chloroesters with TiCl4 and Imidazole in Ethyl Acetate
Iranpoor,Zeynizadeh
, p. 582 - 583 (2007/10/03)
Epoxides can be cleaved easily in EtOAc with TiCl4 in the presence of imidazole to afford β-chloroesters with excellent yields and regioselectivity.
Regio and stereocontrolled synthesis of aryl cis aminoalcohols from cis glycols
Lakshman, Mahesh K.,Zajc, Barbara
, p. 2529 - 2532 (2007/10/03)
Reaction of aryl substituted cis diols with α-acetoxyisobutyryl chloride results in the formation of trans vicinal chlorohydrin acetates where the halide is benzylic. Displacement of chloride with azide ion, deprotection of the ester and reduction of the azide furnishes the requisite cis aminoalcohols. This facile four-step procedure results in the exclusive replacement of a benzylic hydroxyl with an amino group, with a net retention of stereochemistry. This set of transformations is generally applicable to a wide variety of cis diols, and the overall yields are excellent.
