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1.
Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (International ed. in English)》2020,59(40):17641-17647
Catalytic enantioselective α‐fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α‐fluorinated carbonyl compounds. Nevertheless, α‐fluorination of α‐nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α‐hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3‐(2‐naphthyl)‐l ‐alanine‐derived amides are highly effective catalysts for the enantio‐ and site‐selective α‐fluorination of N‐(α‐arylacetyl) and N‐(α‐alkylacetyl) 3,5‐dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α‐fluorinated α‐amino acid derivative). α‐Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield. 相似文献
2.
An Alternative to the Classical α‐Arylation: The Transfer of an Intact 2‐Iodoaryl from ArI(O2CCF3)2
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Dr. Zhiyu Jia Dr. Erik Gálvez Prof. Dr. Rosa María Sebastián Prof. Dr. Roser Pleixats Dr. Ángel Álvarez‐Larena Dr. Eddy Martin Prof. Dr. Adelina Vallribera Dr. Alexandr Shafir 《Angewandte Chemie (International ed. in English)》2014,53(42):11298-11301
The α‐arylation of carbonyl compounds is generally accomplished under basic conditions, both under metal catalysis and via aryl transfer from the diaryl λ3‐iodanes. Here, we describe an alternative metal‐free α‐arylation using ArI(O2CCF3)2 as the source of a 2‐iodoaryl group. The reaction is applicable to activated ketones, such as α‐cyanoketones, and works with substituted aryliodanes. This formal C? H functionalization reaction is thought to proceed through a [3,3] rearrangement of an iodonium enolate. The final α‐(2‐iodoaryl)ketones are versatile synthetic building blocks. 相似文献
3.
Due to the chemoselective dehalogenation by SmI2, the addition of a-halomethylsulfones to carbonyl compounds afforded ,β-hydroxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to good yields. The SmI2-mediated addition of gem-dihalomethylsulfones to ketones also afforded α-halo-β-hydroxysulfones in moderate yields. 相似文献
4.
Zirconium(IV) chloride catalyzed efficient one-pot synthesis of β-amino/β-acetamido carbonyl compounds at room temperature is described. In the presence of ZrCl4, the three-component Mannich-type reaction via a variety of in situ generated aldimines, with various ketones, aromatic aldehydes and aromatic amines in ethanol, led to the formation of β-amino carbonyl compounds and the four-component Mannich-type reaction of aromatic aldehydes with various ketones, acetonitrile and acetyl chloride resulted in the corresponding β-acetamido carbonyl compounds in high to excellent yields. This methodology has also been applied towards the synthesis of dimeric β-amino/β-acetamido carbonyl compounds. 相似文献
5.
Akira Ohnuma Tomohiro Nagata Kenichi Komura Hiromune Ando Hideharu Ishihara Mamoru Koketsu 《Journal of heterocyclic chemistry》2015,52(2):513-517
Various 2H‐5,6‐dihydroselenine derivatives were synthesized by the reaction of α‐alkoxy carbonylselenoacetamides with α,β‐unsaturated ketones in the presence of BF3•Et2O. 相似文献
6.
In the presence of catalytic amounts of RhH(PPh3)4, 1,2‐bis(diphenylphosphino)ethane (dppe), and dimethyl disulfide, cyclic and acyclic α‐phenyl ketones reacted with p‐cyano‐α‐methylthioa‐ cetophenone giving α‐methylthio‐α‐phenylketones. The activated catalyst containing dimethyl disulfide was effective for the α‐methylthiolation reaction of these less reactive substrates. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:18–23, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20650 相似文献
7.
Rhodium‐catalyzed Asymmetric Hydrogenation of α‐Dehydroamino Ketones: A General Approach to Chiral α‐amino Ketones
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Rhodium/DuanPhos‐catalyzed asymmetric hydrogenation of aliphatic α‐dehydroamino ketones has been achieved and afforded chiral α‐amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β‐amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α‐amino ketones and chiral β‐amino alcohols. 相似文献
8.
Hai‐Tao Tang Yun‐Bing Zhou Yu Zhu Hong‐Chao Sun Min Lin Prof. Zhuang‐Ping Zhan 《化学:亚洲杂志》2014,9(5):1278-1281
An efficient Cs2CO3‐promoted synthesis of α‐amino ketones using hydrazines, aldehydes, and α‐haloketones as starting materials through a cascade condensation/nucleophilic substitution/N? N bond cleavage route is developed. The carbonyl group plays a key role in this novel N? N bond cleavage process. 相似文献
9.
Palladium‐Catalyzed Oxidative Difunctionalization of Alkenes with α‐Carbonyl Alkyl Bromides Initiated through a Heck‐type Insertion: A Route to Indolin‐2‐ones
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Jian‐Hong Fan Wen‐Ting Wei Ming‐Bo Zhou Dr. Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(26):6650-6654
The oxidative interception of various σ‐alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium‐catalyzed oxidative difunctionalization reaction of alkenes with α‐carbonyl alkyl bromides is described, in which the σ‐alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp2)? H bond. This method can be applied to various α‐carbonyl alkyl bromides, including primary, secondary, and tertiary α‐bromoalkyl esters, ketones, and amides. 相似文献
10.
Jianfeng Zhang Yadan Wang Zhanwei Cui Fei Wang Zhiwei Miao Ruyu Chen 《Heteroatom Chemistry》2008,19(6):596-601
An efficient and green method to the synthesis of N‐protected o‐hydroxylphenyl α‐amino‐alkylphosphonic monoesters is described. It consists of the three‐component Mannich‐type reaction of phosphoramides, carbonyl compounds (aldehydes or ketones), and 2‐chlorobenzo[1,3,2] diox‐aphospholes under solvent‐free and catalyst‐free conditions, followed by hydrolysis. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:596–601, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20483 相似文献
11.
AgF‐Mediated Fluorinative Cross‐Coupling of Two Olefins: Facile Access to α‐CF3 Alkenes and β‐CF3 Ketones
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Dr. Bing Gao Dr. Yanchuan Zhao Prof. Dr. Jinbo Hu 《Angewandte Chemie (International ed. in English)》2015,54(2):638-642
A AgF‐mediated fluorination with a concomitant cross‐coupling between a gem‐difluoroolefin and a non‐fluorinated olefin is reported. This highly efficient method provides facile access to both α‐CF3 alkenes and β‐CF3 ketones, which otherwise remain challenging to be directly prepared. The application of this method is further demonstrated by the synthesis of bioactive isoxazoline derivatives. This approach represents a conceptually novel route to trifluoromethylated compounds that combines the in situ generation of the CF3 moiety and a C? H functionalization in a single reaction system. 相似文献
12.
Xiu‐Long Yang Jia‐Dong Guo Hongyan Xiao Ke Feng Bin Chen Chen‐Ho Tung Li‐Zhu Wu 《Angewandte Chemie (International ed. in English)》2020,59(13):5365-5370
Radical formation is the initial step for conventional radical chemistry. Reported herein is a unified strategy to generate radicals in situ from aromatic β‐ketoesters by using a photocatalyst. Under visible‐light irradiation, a small amount of photocatalyst fac‐Ir(ppy)3 generates a transient α‐carbonyl radical and persistent ketyl radical in situ. In contrast to the well‐established approaches, neither stoichiometric external oxidant nor reductant is required for this reaction. The synthetic utility is demonstrated by pinacol coupling of ketyl radicals and benzannulation of α‐carbonyl radicals with alkynes to give a series of highly substituted 1‐naphthols in good to excellent yields. The readily available photocatalyst, mild reaction conditions, broad substrate scope, and high functional‐group tolerance make this reaction a useful synthetic tool. 相似文献
13.
Xu Liu Zhaobin Han Zheng Wang Kuiling Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):2009-2013
Optically active medium‐sized cyclic carbonyl compounds bearing an α‐chiral carbon center are of interest in pharmaceutical sciences and asymmetric synthesis. Herein, SpinPhox/IrI catalysts have been demonstrated to be highly enantioselective in the asymmetric hydrogenation of the CC bonds in the exocyclic α,β‐unsaturated cyclic carbonyls, including a broad range of α‐alkylidene lactams, unsaturated cyclic ketones, and lactones. It is noteworthy that the procedure can be successfully used in the asymmetric hydrogenation of the challenging α‐alkylidenelactam substrates with six‐ or seven‐membered rings, thus affording the corresponding optically active carbonyl compounds with an α‐chiral carbon center in generally excellent enantiomeric excesses (up to 98 % ee). Synthetic utility of the protocol has also been demonstrated in the asymmetric synthesis of the anti‐inflammatory drug loxoprofen and its analogue, as well as biologically important ε‐aminocaproic acid derivatives. 相似文献
14.
PPh3⋅HBr‐DMSO Mediated Expedient Synthesis of γ‐Substituted β,γ‐Unsaturated α‐Ketomethylthioesters and α‐Bromo Enals: Application to the Synthesis of 2‐Methylsulfanyl‐3(2 H)‐furanones
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Kanchan Mal Abhinandan Sharma Dr. Prakas R. Maulik Dr. Indrajit Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):662-667
An efficient chemoselective general procedure for the synthesis of γ‐substituted β,γ‐unsaturated α‐ketomethylthioesters from α,β‐unsaturated ketones has been achieved through an unprecedented PPh3?HBr‐DMSO mediated oxidative bromination and Kornblum oxidation sequence. The newly developed reagent system serves admirably for the synthesis of α‐bromoenals from enals. Furthermore, AuCl3‐catalyzed efficient access to 3(2H)‐furanones from the above intermediates under extremely mild conditions are described. 相似文献
15.
Borane‐Catalyzed Reductive α‐Silylation of Conjugated Esters and Amides Leaving Carbonyl Groups Intact
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Youngchan Kim Prof. Dr. Sukbok Chang 《Angewandte Chemie (International ed. in English)》2016,55(1):218-222
Described herein is the development of the B(C6F5)3‐catalyzed hydrosilylation of α,β‐unsaturated esters and amides to afford synthetically valuable α‐silyl carbonyl products. The α‐silylation occurs chemoselectively, thus leaving the labile carbonyl groups intact. The reaction features a broad scope of both acyclic and cyclic substrates, and the synthetic utility of the obtained α‐silyl carbonyl products is also demonstrated. Mechanistic studies revealed two operative steps: fast 1,4‐hydrosilylation of conjugated carbonyls and then slow silyl group migration of a silyl ether intermediate. 相似文献
16.
Boris Minkovich Ilya Ruderfer Alexander Kaushansky Dr. Dmitry Bravo‐Zhivotovskii Prof. Yitzhak Apeloig 《Angewandte Chemie (International ed. in English)》2018,57(40):13261-13265
The first two α‐sila‐dipeptides, 7 and cyclo‐sila‐dipeptide 8 , were synthesized and characterized by several methods, including X‐ray crystallography. Bulky t‐BuMe2Si substituents provide some kinetic stabilization to the synthesized molecules. 7 and 8 are the first examples of a “Si for C switch” in the central α‐position of an amino acid or a peptide, in which silicon is bonded to both the amino and the carbonyl groups. 相似文献
17.
Birgit Prüger Dr. Gretchen E. Hofmeister Prof. Dr. Christian Borch Jacobsen David G. Alberg Prof. Dr. Martin Nielsen Dr. Karl Anker Jørgensen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(12):3783-3790
Transition‐metal‐free formal Sonogashira coupling and α‐carbonyl arylation reactions have been developed. These transformations are based on the nucleophilic aromatic substitution (SNAr) of β‐carbonyl sulfones to electron‐deficient aryl fluorides, producing a key intermediate that, depending on the reaction conditions, gives the aromatic alkynes or α‐aryl carbonyl compounds. The development of these reactions is presented and, based on investigations under basic and acidic conditions, mechanisms have been proposed. To develop the formal Sonogashira coupling further, a milder, two‐step protocol is also disclosed that expands the reaction concept. The scope of these reactions is demonstrated for the synthesis of Sonogashira and α‐carbonyl arylated products from a range of electron‐deficient aryl fluorides with a variety of functional groups and aryl‐, heteroaryl‐, alkyl‐, and alkoxy‐substituted sulfone nucleophiles. These transition‐metal‐free reactions complement the metal‐catalyzed versions in terms of substitution patterns, simplicity, and reaction conditions. 相似文献
18.
Hadgu Girmay Gebreslasie
yvind Jacobsen Carl Henrik Grbitz 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(8):o283-o287
The title compound (systematic name: methyl 2‐{2‐[(tert‐butoxycarbonyl)amino]‐2‐methylpropanamido}‐2‐methylpropanoate), C14H26N2O5, (I), crystallizes in the monoclinic space group P21/n in two polymorphic forms, each with one molecule in the asymmetric unit. The molecular conformation is essentially the same in both polymorphs, with the α‐aminoisobutyric acid (Aib) residues adopting ϕ and ψ values characteristic of α‐helical and mixed 310‐ and α‐helical conformations. The helical handedness of the C‐terminal residue (Aib2) is opposite to that of the N‐terminal residue (Aib1). In contrast to (I), the closely related peptide Boc‐Aib‐Aib‐OBn (Boc is tert‐butoxycarbonyl and Bn is benzyl) adopts an αL‐PII backbone conformation (or the mirror image conformation). Compound (I) forms hydrogen‐bonded parallel β‐sheet‐like tapes, with the carbonyl groups of Aib1 and Aib2 acting as hydrogen‐bond acceptors. This seems to represent an unusual packing for a protected dipeptide containing at least one α,α‐disubstituted residue. 相似文献
19.
Copper‐Catalyzed Dehydrogenative Cross‐Coupling Reaction between Allylic CH Bonds and α‐CH Bonds of Ketones or Aldehydes
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Xing‐Fen Huang Muhammad Salman Prof. Zhi‐Zhen Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6618-6621
A dehydrogenative cross‐coupling reaction between allylic C?H bonds and the α‐C?H bond of ketones or aldehydes was developed using Cu(OTf)2 as a catalyst and DDQ as an oxidant. This synthetic approach to γ,δ‐unsaturated ketones and aldehydes has the advantages of broad scope for both ketones and aldehydes as reactants, mild reaction conditions, good yields and atom economy. A plausible mechanism using Cu(OTf)2 as a Lewis acid catalyst was also proposed (DDQ=2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone; Tf=trifluoromethanesulfonate). 相似文献
20.
Oxidative Difunctionalization of Alkenyl MIDA Boronates: A Versatile Platform for Halogenated and Trifluoromethylated α‐Boryl Ketones
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Wen‐Xin Lv Yao‐Fu Zeng Dr. Qingjiang Li Dr. Yunyun Chen Dong‐Hang Tan Ling Yang Prof.Dr. Honggen Wang 《Angewandte Chemie (International ed. in English)》2016,55(34):10069-10073
The synthesis of halogenated and trifluoromethylated α‐boryl ketones via a one‐pot oxidative difunctionalization of alkenyl MIDA boronates is reported. These novel densely functionalized organoborons bearing synthetically and functionally valuable carbonyl, halogen/CF3 and boronate moieties within the same molecule are synthetically challenging for the chemist, but have great synthetic potential, as demonstrated by their applications in a straightforward synthesis of borylated furans. The generality of this reaction was extensively investigated. This reaction is attractive since the starting materials, alkenyl MIDA boronates, are easily accessible. 相似文献