1496-00-0Relevant academic research and scientific papers
Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
supporting information, p. 16490 - 16494 (2019/11/03)
Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
Cross-Coupling of Phenol Derivatives with Umpolung Aldehydes Catalyzed by Nickel
Lv, Leiyang,Zhu, Dianhu,Tang, Jianting,Qiu, Zihang,Li, Chen-Chen,Gao, Jian,Li, Chao-Jun
, p. 4622 - 4627 (2018/05/22)
A nickel-catalyzed cross-coupling to construct the C(sp2)-C(sp3) bond was developed from two sustainable biomass-based feedstocks: phenol derivatives with umpolung aldehydes. This strategy features the in situ generation of moisture/air-stable hydrazones from naturally abundant aldehydes, which act as alkyl nucleophiles under catalysis to couple with readily available phenol derivatives. The avoidance of using both halides as the electrophiles and organometallic or organoboron reagents (also derived from halides) as the nucleophiles makes this method more sustainable. Water tolerance, great functional group (ketone, ester, free amine, amide, etc.) compatibility, and late-stage elaboration of complex biological molecules exemplified its practicability and unique chemoselectivity over organometallic reagents.
Nickel-catalyzed cross-coupling of aldehydes with aryl halides: Via hydrazone intermediates
Tang, Jianting,Lv, Leiyang,Dai, Xi-Jie,Li, Chen-Chen,Li, Lu,Li, Chao-Jun
supporting information, p. 1750 - 1753 (2018/02/21)
Traditional cross-couplings require stoichiometric organometallic reagents. A novel nickel-catalyzed cross-coupling reaction between aldehydes and aryl halides via hydrazone intermediates has been developed, merging the Wolff-Kishner reduction and the classical cross-coupling reactions. Aromatic aldehydes, aryl iodides and aryl bromides are especially effective in this new cross-coupling chemistry.
Cobalt-Catalyzed Reductive Cross-Coupling Between Benzyl Chlorides and Aryl Halides
Pal, Suman,Chowdhury, Sushobhan,Rozwadowski, Elodie,Auffrant, Audrey,Gosmini, Corinne
supporting information, p. 2431 - 2435 (2016/08/16)
A new protocol for the direct reductive cobalt-catalyzed arylation of benzyl chlorides has been developed in order to form functionalized diarylmethanes. A variety of reactive groups either on the aryl or the benzyl halide was employed. This represents the first cobalt-catalyzed reductive cross-coupling which does not require any ligand and pyridine. A reaction pathway is proposed involving a radical benzyl species. (Figure presented.).
N-Heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed Suzuki-Miyaura coupling of benzyl carbamates with arylboronic acids
Wang, Xiao-Xia,Luo, Mao-Jun,Lu, Jian-Mei
, p. 11438 - 11444 (2015/12/04)
The Suzuki-Miyaura coupling of benzyl carbamates with arylboronic acids was achieved in an environmentally benign medium. Using water as the sole solvent, such transformation took place very well to give the desired diarylmethane derivatives in good to almost quantitative yields in the presence of a well-defined NHC-Pd(ii)-Im complex under mild conditions. It is worth noting here that this is the first example of benzyl carbamates used in coupling reaction, thus affording a new method for the formation of diarylmethanes by palladium-catalyzed C-O bond activation.
Synthesis of diarylmethanes through palladium-catalyzed coupling of benzylic phosphates with arylsilanes
Zhang, Pengbo,Xu, Jian,Gao, Yuzhen,Li, Xueqin,Tang, Guo,Zhao, Yufen
, p. 2928 - 2932 (2015/01/16)
An efficient approach to the benzylation of arenes has been developed. The reactions described provide straightforward access to diarylmethanes through Pd-catalyzed coupling of benzylic phosphates with arylsilanes in good to excellent yields. The reaction tolerates a wide range of functionalities such as halide, alkoxyl, and nitro groups.
Direct electrosynthesis of ketones from benzylic methylenes by electrooxidative C-H activation
Meng, Li,Su, Jihu,Zha, Zhenggen,Zhang, Li,Zhang, Zhenlei,Wang, Zhiyong
supporting information, p. 5542 - 5545 (2013/05/23)
Electrify your chemistry! Direct electrosynthesis of ketones from benzylic methylenes in an undivided cell was realized in moderate to good yields (see scheme). In this electrosynthesis, electrons instead of conventional oxidants and catalysts are employed to make the reaction environmentally benign. Moreover, the reaction intermediate radical was detected by ESR spectroscopy and the reaction mechanism was clarified.
Nickel-catalyzed cross couplings of benzylic ammonium salts and boronic acids: Stereospecific formation of diarylethanes via C-N bond activation
Maity, Prantik,Shacklady-Mcatee, Danielle M.,Yap, Glenn P. A.,Sirianni, Eric R.,Watson, Mary P.
supporting information, p. 280 - 285 (2013/02/25)
We have developed a nickel-catalyzed cross coupling of benzylic ammonium triflates with aryl boronic acids to afford diarylmethanes and diarylethanes. This reaction proceeds under mild reaction conditions and with exceptional functional group tolerance. Further, it transforms branched benzylic ammonium salts to diarylethanes with excellent chirality transfer, offering a new strategy for the synthesis of highly enantioenriched diarylethanes from readily available chiral benzylic amines.
Synthesis of diarylmethane derivatives from Stille cross-coupling reactions of benzylic halides
Nichele, Tatiana Z.,Monteiro, Adriano L.
, p. 7472 - 7475 (2008/03/14)
A catalyst precursor prepared in situ from palladium acetate and a phosphine ligand was used for the Stille cross-coupling reaction of benzylic bromides and chlorides with aryltributyltin analogues. The reactions were performed at 80 °C using dppf as ligand in the presence of KF, or more conveniently using PPh3 in the absence of base, furnishing diarylmethane derivatives in high yields (86-99%). Using Pd(OAc)2/PPh3 as catalyst precursor competitive Stille and Suzuki cross-coupling reactions with benzyl chloride showed that in the absence of base or in the presence of KF the Stille product is the majority product, and only the Suzuki product was obtained in the presence of KOH as base.
