- α,α-Diarylethylene Glycols as Valuable Precursor for Synthesis of 1,1-Diarylethenes and α,α-Diaryl Acetaldehydes
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Towards assembling of diarylmethine unit present in biologically important molecules, we have developed a new Weinreb Amide (WA) based building block derived from glycolic acid. The WA functionality present in this building block permits the sequential addition of various arylmagnesium bromide reagents in a controlled manner that enables assembly of a diarylmethine unit. The developed synthetic route provides easy access to important diarylethenes and α,α-diarylethylene glycols. The synthesized α,α-diarylethylene glycols provide access to synthetically important symmetrical and unsymmetrical α,α-diaryl acetaldehydes as valuable intermediates.
- Tiwari, Praveen Kumar,Sivaraman, Balasubramaniam,Aidhen, Indrapal Singh
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p. 3594 - 3605
(2017/07/22)
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- Palladium-Catalyzed Chemo- and Enantioselective C?O Bond Cleavage of α-Acyloxy Ketones by Hydrogenolysis
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A chemoselective C?O bond cleavage of the ester alkyl side-chain of α-acyloxy ketones was realized for the first time by a highly efficient palladium-catalyzed hydrogenolysis (S/C=6000, the highest catalytic efficiency by far). Furthermore, a kinetic resolution of α-acyloxy ketones was first developed by enantioselective hydrogenolysis with good yields and up to 99 % ee.
- Chen, Jianzhong,Zhang, Zhenfeng,Liu, Delong,Zhang, Wanbin
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p. 8444 - 8447
(2016/07/19)
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- Synergistic interplay of a non-heme iron catalyst and amino acid coligands in H2O2 activation for asymmetric epoxidation of α-alkyl-substituted styrenes
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Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97% ee) in short reaction times.
- Cuss, Olaf,Ribas, Xavi,Lloret-Fillol, Julio,Costas, Miquel
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supporting information
p. 2729 - 2733
(2015/03/04)
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- Palladium-catalyzed asymmetric hydrogenation of α-acyloxy-1- arylethanones
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First hand: The first example of a palladium-catalyzed asymmetric hydrogenation of α-acyloxy ketones (1) was accomplished to give the hydrogenated products 2 with by far the highest catalytic efficiency in up to quantitative conversions and excellent enantioselectivities. The hydrogenated products could serve as important intermediates for the preparation of many drug candidates. TFE=2,2,2-trifluoroethanol. Copyright
- Chen, Jianzhong,Liu, Delong,Butt, Nicholas,Li, Chao,Fan, Dongyang,Liu, Yangang,Zhang, Wanbin
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p. 11632 - 11636
(2013/11/06)
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- Arylation of α-pivaloxyl ketones with arylboronic reagents via Ni-catalyzed sp3 C-O activation
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A Suzuki-Miyaura coupling of α-pivaloxyl ketones via Ni-catalyzed sp3 C-O activation to produce α-aryl ketones is developed. This study offers a convenient method to construct α-arylation products from readily available α-hydroxyl carbonyl compounds.
- Huang, Kun,Li, Gang,Huang, Wei-Ping,Yu, Da-Gang,Shi, Zhang-Jie
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supporting information; experimental part
p. 7224 - 7226
(2011/08/09)
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- A convenient and versatile method for the preparation of α-hydroxymethyl ketone derivatives from the corresponding allyl silyl ethers or allyl carboxylates
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The ozonolysis of 1-substituted allyl silyl ethers or 1-substituted allyl carboxylates followed by treatment with bases gave the corresponding α-silyloxymethyl- or α-acyloxymethyl-ketones in good yields. It is proposed to proceed via the corresponding α-silyloxy- or α-acyloxyaldehydes intermediates followed by 1,4-group migration. The results of theoretical calculations are applicable to explain the experimental results.
- Hon, Yung-Son,Wong, Ying-Chieh,Wu, Kuo-Jui
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experimental part
p. 896 - 914
(2009/12/06)
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- Enantioselective synthesis of α-tertiary hydroxyaldehydes by palladium-catalyzed asymmetric allylic alkylation of enolates
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Chiral α-tertiary hydroxyaldehydes are very versatile building blocks in synthetic chemistry. Herein, we report the first examples of a catalytic asymmetric protocol for the synthesis of such compounds from readily available α-halo or α-hydroxy ketones or enol silyl ethers with excellent yields and enantioselectivity. Its synthetic utility is demonstrated in the short, efficient formal synthesis of (S)-oxybutynin. In this process, the chiral ligand controls the regioselectivity as well as the enantioselectivity. Copyright
- Trost, Barry M.,Xu, Jiayi,Reichle, Markus
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p. 282 - 283
(2007/10/03)
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- Synthetic applications of the amine-base treatment in the ozonolysis of substituted-allyl silyl ethers or -allyl esters via a novel ene-diol type rearrangement
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The ozonolysis of substituted-allyl silyl ethers or -allyl esters followed by treatment with bases gave the corresponding α-silyloxy ketones or α-acyloxy ketones in good yields. The reaction is proposed to proceed via a novel ene-diol rearrangement of the corresponding α-silyloxy aldehydes or α-acyloxy aldehydes intermediates.
- Hon, Yung-Son,Wong, Ying-Chieh
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p. 1365 - 1368
(2007/10/03)
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- Preparation and Reactivity of Highly Functionalized Organometallics at the α Position of Oxygen or Nitrogen
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α-Halogenoalkyl carboxylates (FG-R1CH(X)(OCOR2); FG = COOR, CN, SR; X = I, Br) were readily prepared by the addition of an acid chloride or bromide (R2COX; X = Br or Cl) to an aldehyde (FG-RCHO) in the presence of a catalytic amount of ZnCl2.They insert efficiently zinc dust in THF-DMSO (X = Br, 8 - 10 deg C, 6 - 10 h) affording the corresponding zinc organometallics at the α position to oxygen FG-RCH(ZnBr)(OAc).After the addition of the THF-soluble copper salt CuCN*2LiCl, the corresponding copper reagents FG-RCH(Cu(CN)ZnBr)(OAc) are formed and reacted with variousclasses of electrophiles such as acid chlorides, aldehydes, enones, allylic and alkynyl halides, activated alkynes, nitro olefins and alkylidenemalonates providing polyfunctional molecules in excellent yields.Similarly, zinc organometallics at the α position to the nitrogen of cyclic imides were prepared by the zinc insertion to cyclic α-chloromethyl (or α-chloroethyl) imides.After their transmetalation to the corresponding copper organometallic ((R1CO)2NCH(R)(Cu(CN)ZnCl); R = Me or H), they were reacted with allylic and alkynyl halides and ethyl propiolate affording polyfunctional imides.The reaction of cyclic N-(chloromethyl)imides with aldehydes in the presence of chromium(II) chloride in THF furnishes protected amino alcohols in 36 - 95percent yield.
- Knochel, Paul,Chou, Tso-Sheng,Jubert, Carole,Rajagopal, Duddu
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p. 588 - 599
(2007/10/02)
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- Nucleophilic Reactivity of Zinc and Copper Carbenoids. 2
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The rectivity of the new zinc and copper carbenoids PivOCH2Cu(CN)ZnI (4) and ICH2Cu*ZnI2 (5) toward various electrophiles has been investigated.Of special interest is the direct and highly stereoselective conversion of allylic bromides to the corresponding homoallylic iodides by using the reagent ICH2Cu*ZnI2
- Knochel, Paul,Chou, Tso-Sheng,Chen, Huai Gu,Yeh, Ming Chang P.,Rozema, Michael J.
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p. 5202 - 5204
(2007/10/02)
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- α-Oxygenation of Aldehydes and Cyclic Ketones by Acylation-Rearrangement of Nitrones
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The reaction of N-tert-butylnitrones (1a-e) of aldehydes and N-methylnitrones (2 and 3) of cyclic ketones with acid chlorides in the presence of triethylamine afforded α-acyloxy imines by rearrangement of N-vinyl-O-acylhydroxylamine intermediates.Hydrolysis of the α-acyloxy imines gave α-acyloxy aldehydes and ketones.The acylation-rearrangement reaction offers a new method for α-oxygenation of carbonyl compounds.
- Cummins, Clark H.,Coates, Robert M.
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p. 2070 - 2076
(2007/10/02)
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