20498-63-9Relevant academic research and scientific papers
C-H Alkylation of Aldehydes by Merging TBADT Hydrogen Atom Transfer with Nickel Catalysis
Murugesan, Vetrivelan,Ganguly, Anirban,Karthika, Ardra,Rasappan, Ramesh
, p. 5389 - 5393 (2021/07/21)
Catalyst controlled site-selective C-H functionalization is a challenging but powerful tool in organic synthesis. Polarity-matched and sterically controlled hydrogen atom transfer (HAT) provides an excellent opportunity for site-selective functionalization. As such, the dual Ni/photoredox system was successfully employed to generate acyl radicals from aldehydes via selective formyl C-H activation and subsequently cross-coupled to generate ketones, a ubiquitous structural motif present in the vast majority of natural and bioactive molecules. However, only a handful of examples that are constrained to the use of aryl halides are developed. Given the wide availability of amines, we developed a cross-coupling reaction via C-N bond cleavage using the economic nickel and TBADT catalyst for the first time. A range of alkyl and aryl aldehydes were cross-coupled with benzylic and allylic pyridinium salts to afford ketones with a broad spectrum of functional group tolerance. High regioselectivity toward formyl C-H bonds even in the presence of α-methylene carbonyl or α-amino/oxy methylene was obtained.
Visible-light-induced oxidative lignin c-c bond cleavage to aldehydes using vanadium catalysts
Liu, Huifang,Li, Hongji,Luo, Nengchao,Wang, Feng
, p. 632 - 643 (2020/01/02)
Lignin is the largest carrier of aromatics on earth, and its depolymerization can afford value-Added aromatic products. Direct cleavage of the C-C bonds in lignin linkages is significant, but it is challenging to obtain low-molecular-weight aromatic monomers. Herein, using vanadium catalysts under visible light, we selectively cleave the C-C bonds in β-1 and β-O-4 interlinkages occluded in lignin models and extracts by an oxidative protocol. Visible light irradiation triggered single electron transfer between the substrate and the catalyst, which further induced the selective Cα-Cβ bond cleavage and generated the final aromatic products through radical intermediates. Using this photocatalytic chemistry, the reactivity of lignin models and the selectivity of Cα-Cβ bond cleavage were significantly improved. More importantly, this protocol affords aromatic monomers through the fragmentation of organosolv lignins even at room temperature, indicating the potential of photocatalytic C-C bond cleavage of lignin linkages under ambient conditions.
Enantioselective 1,2-Anionotropic Rearrangement of Acylsilane through a Bisguanidinium Silicate Ion Pair
Cao, Weidi,Tan, Davin,Lee, Richmond,Tan, Choon-Hong
, p. 1952 - 1955 (2018/02/17)
Highly enantioselective bisguanidinium-catalyzed tandem rearrangements of acylsilanes are reported. The acylsilanes were activated via an addition of fluoride on the silicon to form a penta-coordinate anionic silicate intermediate. The silicate then underwent alkyl or aryl group migration from the silicon atom to the neighboring carbonyl carbon atom (1,2-anionotropic rearrangement), followed by [1,2]-Brook rearrangement to provide the secondary alcohols in high yields with excellent enantioselectivities (up to 95% ee). The isolation of an α-silylcarbinol intermediate as well as DFT calculations revealed that the 1,2-anionotropic rearrangement occurred via a bisguanidinium silicate ion pair, which is the stereodetermining step. The chiral center formed is then retained without inversion through the subsequent [1,2]-Brook rearrangement. Crotyl acylsilanes were smoothly transformed into homoallylic linear crotyl alcohols with retention of E/Z geometry, and no branched alcohols were detected. This clearly suggested that the 1,2-anionotropic rearrangement occurred through a three-membered instead of a five-membered transition state.
Pd-Catalyzed Conjunctive Cross-Coupling between Grignard-Derived Boron “Ate” Complexes and C(sp2) Halides or Triflates: NaOTf as a Grignard Activator and Halide Scavenger
Lovinger, Gabriel J.,Aparece, Mark D.,Morken, James P.
supporting information, p. 3153 - 3160 (2017/03/11)
Catalytic enantioselective conjunctive cross-couplings that employ Grignard reagents are shown to furnish an array of nonracemic chiral organoboronic esters in an efficient and highly selective fashion. The utility of sodium triflate in facilitating this reaction is two-fold: it enables “ate” complex formation and overcomes catalytic inhibition by halide ions.
Catalyst-controlled highly selective coupling and oxygenation of olefins: A direct approach to alcohols, ketones, and diketones
Su, Yijin,Sun, Xiang,Wu, Guolin,Jiao, Ning
supporting information, p. 9808 - 9812 (2013/09/23)
Oxygen? That's radical! A method for the direct synthesis of substituted alcohols, ketones, and diketones through a catalyst-controlled highly chemoselective coupling and oxygenation of olefins has been developed. The method is simple and practical, can be switched by the selection of different catalysts, and employs molecular oxygen as both an oxidant and a reagent. Copyright
Nickel-catalyzed cross-coupling of styrenyl epoxides with boronic acids
Nielsen, Daniel K.,Doyle, Abigail G.
supporting information; scheme or table, p. 6056 - 6059 (2011/09/13)
Let's get multicatalytic! A Ni0 catalyst complexed with a biaryldialkyl monophosphine ligand facilitates C-C bond formation between styrenyl epoxides and aryl boronic acids (see scheme). X-ray analysis of a catalytically active nickel/ligand complex supports a redox pathway involving C sp 3-O bond activation. A variety of α-substituted alcohols were generated with good reaction efficiency by a multicatalytic sequence. Copyright
A practical method to stereospecifically synthesize trans-stilbene derivatives
Jian, Yujuan,Sun, Gaojun,Li, Jiaming,Su, Dan,Li, Chuanrun,Zhong, Guochen
, p. 1423 - 1428 (2011/10/31)
A practical method to stereospecifically synthesize trans-stilbenes was developed via the one-pot benzylation-dehydration reaction of aromatic aldehydes with benzyltrimethylsilane (BTMS), which was driven by tetrabutylammonium fluoride (TBAF) in THF. At the same time a plausible description of the whole process was proposed and the effects of substituted groups on the reaction were investigated. Also this method was employed to synthesize three precursors of natural products with excellent yields, which demonstrated that this method is much efficient and practical in the synthesis of some natural products. A practical method to stereospecifically synthesize trans-stilbenes was developed via the one-pot benzylation-dehydration reaction of aromatic aldehydes with benzyltrimethylsilane, which was driven by tetrabutylammonium fluoride in THF. A plausible description of the whole process was proposed and the effects of substituted groups on the reaction were investigated. This method was employed to synthesize three precursors of natural products with excellent yields. Copyright
Regioselective ring-opening reaction of unsymmetrical 2,3-diaryl epoxides via catalytic hydrogenolysis with Pd(0)EnCatTM
Kimachi, Tetsutaro,Nagata, Hiroyo,Kobayashi, Yusuke,Takahashi, Kaori,Torii, Eri,Ju-Ichi, Motoharu
experimental part, p. 365 - 368 (2011/04/15)
A series of unsymmetrical 2,3-diaryl epoxides were hydrogenated under transfer-hydrogenation conditions using the polyurea-encapsulated palladium catalyst [Pd(0)EnCatTM]. The position of the cleaved C-O bond was determined by 1H NMR analysis of the ring-opened products derived from the epoxide, in which one of the two benzylic methyne protons is deuterated. The ratio of ring-opened products of the unsymmetrically substituted 2,3-diaryl epoxides was affected by the degree of the steric bulkiness on the aromatic ring. Georg Thieme Verlag Stuttgart New York.
The leaving group dependence in the rates of solvolysis of 1,2-diphenylethyl system
Santhosh Kumara,Jayakumarb,Balachandranc
scheme or table, p. 783 - 788 (2011/05/05)
1,2-Diphenylethyl chloride undergoes solvolysis by SN1 mechanism in aqueous organic solvents. The α-phenyl group of 1,2-diphenylethyl chloride enters into conjugation with the developing carbocationic centre. The β-phenyl group on the other hand was unable to extend its conjugation via neighbouring group participation due to steric inhibition of resonance in the formation of non-classical carbocation. 1,2-Diphenylethyl chloride thus behaves similar to 1-phenylethyl chloride in its solvolysis pattern. The solvolytic rate studies of chloride and methanesulphonate of 1,2-diphenylethyl alcohol in various aqueous organic solvents show that the dispersion observed in the Winstein- Grunwald plot is not due to a change in leaving group but due to the difference in solvation requirements of aromatic and aliphatic groups. Copyright
