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1.
Hans Choi Harry J. Shirley Paul A. Hume Margaret A. Brimble Daniel P. Furkert 《Angewandte Chemie (International ed. in English)》2017,56(26):7420-7424
The unexpected synthesis of industrially important N-vinyl amides directly from aldehydes and α,β-unsaturated N-vinyl amides from esters is reported. This reaction probably proceeds through an initial [3+2] azide–enolate cycloaddition involving a vinyl azide generated in situ. A survey of the reaction scope and preliminary mechanistic findings supported by quantum computational analysis are reported, with implications for the future development of atom-efficient amide synthesis. Intriguingly, this study suggests that (cautious) reevaluation of azidoethene as a synthetic reagent may be warranted. 相似文献
2.
The [4+2] reactions of N‐acyliminium ions, produced from 2‐aryl‐3‐hydroxy‐2,3‐dihydroisoindol‐1‐ones or 5‐hydroxy‐1‐phenyl‐2,5‐dihydro/2,3,4,5‐tetrahydropyrrol‐2‐ones in the presence of BF3OEt2, with α,β‐unsaturated ketones or esters were examined, and the dependence of these reactions on the substituents at double bonds was clarified. For β‐aryl substituted α,β‐unsaturated ketones and esters such as 4‐aryl‐3‐buten‐2‐ones, chalcones and methyl cinnamate, the [4+2] reactions could proceed smoothly at room temperature to afford 6‐acyl‐5,6,6a,11‐tetrahydroisoindolo[2,1‐a]quinolin‐11‐ones and 4‐acyl‐1,3a,4,5‐tetrahydropyrrolo[1,2‐a]quinolin‐ 1‐ones or 4‐acyl‐1,2,3,3a,4,5‐hexahydropyrrolo[1,2‐a]quinolin‐1‐ones in moderate to high yields; while for simple α,β‐unsaturated ketones and esters such as methyl crotonate and ethyl 3‐methylbut‐2‐enoate, except mesityloxide, the [4+2] reactions were difficult to proceed. The cycloaddition reactions were highly stereoselective, and only one stereoisomer was produced in each reaction. 相似文献
3.
4.
Dr. Wei Wen Tan Yew Jin Ong Prof. Naohiko Yoshikai 《Angewandte Chemie (International ed. in English)》2017,56(28):8240-8244
A copper-catalyzed condensation reaction of oxime acetates and α,β-unsaturated ketimines to give pyridine derivatives is reported. The reaction features mild conditions, high functional-group compatibility, and high regioselectivity with respect to unsymmetrical oxime acetates, thus allowing the preparation of a wide range of polysubstituted pyridines, many of which are not readily accessible by conventional condensation methods. 相似文献
5.
Zhengyu Li Yizhi Zhang Dr. Yunxiao Zhang Xingyi He Prof. Dr. Xiao Shen 《Angewandte Chemie (International ed. in English)》2023,62(20):e202303218
Monofluoroalkenes are nonhydrolyzable mimetics of amides. Previous work focused on the synthesis of non-cyclic monofluoroalkenes. However, diastereoselective synthesis of monofluorocyclohexenes from non-cyclic substrates is challenging. Herein, we report the first photocatalyzed cascade cyclization reactions of readily available α,β-unsaturated carbonyl compounds and gem-difluoroalkenes for the synthesis of highly functionalized monofluorocyclohexenes. The reaction shows broad substrate scope with high diastereoselectivity (>30 examples, up to 86 % yield, >20 : 1 dr). The post-reaction transformations of the products demonstrate the synthetic potential of this methodology. 相似文献
6.
A [4+2] cycloaddition of α,β-unsaturated imines and isocyanates catalyzed by a phosphoramidite-rhodium complex provides pyrimidinones in good yields and high enantioselectivities. 相似文献
7.
Acylation of an enamine followed by acid hydrolysis constitutes the well-known Stork's reaction of synthesizing β-diketones.1,2 This article reports that the acylated enamine 1 which corresponds to monoenamine of a β-diketone can be hydrogenated to a Mannich base 2 which on elimination by heating or treatment with acid yields the α, β-unsaturated ketone 3; further hydrogenation gives saturated ketone 4 in good yield (Scheme 1). A similar transformation effected by hydroboration has been reported by Montury and Góre. 相似文献
8.
Yicong Ge Cheng Qin Lu Bai Jiamao Hao Prof. Dr. Jingjing Liu Prof. Dr. Xinjun Luan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19147-19151
A novel [4+1] spiroannulation of o- & p-bromophenols with α,β-unsaturated imines has been developed for the direct synthesis of a new family of azaspirocyclic molecules. Notably, several other halophenols (X=Cl, I) were also applicable for this transformation. Moreover, a catalytic asymmetric version of the reaction was realized with 1-bromo-2-naphthols by using a chiral ScIII/Py-Box catalyst. Mechanistic studies revealed that this domino reaction proceeded through electrophile-triggered dearomatization of phenol derivatives at their halogenated positions and followed by halogen-displacement with N-nucleophiles via a radical-based SRN1 mechanism. 相似文献
9.
A. V. Varlamov A. N. Levov F. Toze A. I. Chernyshev 《Chemistry of Heterocyclic Compounds》2004,40(4):490-495
Condensation of 1-amino-4-azafluorene with -diketones and with unsaturated ketones in basic medium gives novel substituted 1,4-diazafluoranthenes and also dihydro-4-azafluoreno[9,9a,1-b,c]cyclohexano[2',3'-e]- and indano[1',2'-e]azepines. 相似文献
10.
Satoshi Kojima Tsugihiko Hidaka Yuko Ohba Katsuo Ohkata 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):729-732
The Horner-Wadsworth-Emmons reaction of diphenylphosphonoacetamides [(PhO) 2 P(O)CH 2 CONRR'] ( 2a : R, R' = CH 2 Ph; 2b : R = CH 2 Ph, R' = H; 2c : R = Me, R' = OMe) was examined. The reaction of 2a was found to be Z -selective for benzaldehyde with selectivities up to 94:6. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3-phenylpropionaldehyde (87:13), while 2c was somewhat effective only for the latter aldehyde (83:17). 相似文献
11.
Dr. Yujie Liang Fritz Paulus Dr. Constantin G. Daniliuc Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2023,62(34):e202305043
Synthesis of bicyclic scaffolds has attracted tremendous attention because they are playing an important role as saturated bioisosteres of benzenoids in modern drug discovery. Here, we report a BF3-catalyzed [2π+2σ] cycloaddition of aldehydes with bicyclo[1.1.0]butanes (BCBs) to access polysubstituted 2-oxabicyclo[2.1.1]hexanes. A new kind of BCB containing an acyl pyrazole group was invented, which not only significantly facilitates the reactions, but can also serve as a handle for diverse downstream transformations. Furthermore, aryl and vinyl epoxides can also be utilized as substrates which undergo cycloaddition with BCBs after in situ rearrangement to aldehydes. We anticipate that our results will promote access to challenging sp3-rich bicyclic frameworks and the exploration of BCB-based cycloaddition chemistry. 相似文献
12.
1 INTRODUCTION Alkaloids and their derivatives are ubiquitous in natural products, and most of those compounds are of biological activities. Therefore, the structure modifi- cation of alkaloids is always the point that organic chemists and medicinal chemists focus on[1~10]. Qui- nolizine ring system is an important kind of alkaloid, which has a nitrogen atom shared by two six-mem- bered rings. Many medicines have quinolizine ring system, such as reserpine[11, 12] and berberine[13]. How- … 相似文献
13.
α,β-Unsaturated aldimines were specifically oxidized to amides with Oxone in the presence of AlCl3 as a Lewis acid in CH2Cl2. No migration of aryl group occurred in the rearrangement reaction. 相似文献
14.
The [2+3] cycloaddition of Z-C,N-diphenylnitrone with E--nitrostyrenes leads to (3SR, 4SR, 5SR)- and (3SR, 4RS, 5RS)-2,3-diphenyl-4-nitro-5-arylisoxazolidines as the only reaction products. The kinetics of the reaction was studied by using the HPLC method. It was found that total rate constants increase with increasing substituent Hammett -constants. The substituent effect is rationalized in terms of FMO theory. 相似文献
15.
K. A. Frolov V. V. Dotsenko S. G. Krivokolysko E. O. Kostyrko 《Chemistry of Heterocyclic Compounds》2013,49(9):1289-1300
16.
A. A. Pimenov N. V. Makarova I. K. Moiseev M. N. Zemtsova 《Chemistry of Heterocyclic Compounds》2004,40(5):575-581
The influence has been established of the structure of the initial ketone, the reactants, and the reaction conditions on the direction of the interaction of ,-unsaturated ketones of the adamantane series with hydrazine, phenylhydrazine, semicarbazide, thiosemicarbazide, urea, and thiourea. It was found that on interaction with hydrazine and phenylhydrazine both intermediate hydrazones and the final cyclization products, pyrazolines, were formed. Reaction with semicarbazide and thiosemicarbazide leads only to the synthesis of derivatives at the carbonyl group, semicarbazones and thiosemicarbazones, but with urea and thiourea leads to products of addition at the double bond. 相似文献
17.
A synthesis of α-bromo-α,β-unsaturated esters 2 from tert-butyl α-(trimethylsilyl)-α-bromoacetate (1) and carbonyl compounds is described. 相似文献
18.
《中国化学快报》1997,(7)
The[4+3]cycloaddihonreachonofatlyliCcationsanddienesisavodemeIhalfortheconstwhonofseven-memberedrings1.AkCyvariantofemPlOyingacyclicoxyalll,i.e.,anoxyallylembeinring,wouldPrOvidCaconvenientroutetofunctiotaledmdri-eddsyClesandheteIDCycles.Inaddihon,theketobridgeinthecycloadductwouldbeusefulnotonlyinProvthegasultablefUnchonalityforfurtherebohonbutalsoinrigmpingthefiechemedium-edring.Chaandhisco-workershaveemployedthesaPPrOaChtOthesynthesisofnandProductS2.AtpesenLonlyafewexamplesofthisre… 相似文献
19.
Umar Farid Maria Luisa Aiello Prof. Stephen J. Connon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10074-10079
A new catalytic methodology was developed to promote an efficient one-pot kinetic resolution of racemic aldehydes with selectivity (s*) of up to 91 (99:1 d.r., >99 % ee) in a cycloaddition reaction with enolizable anhydrides to afford dihydroisocoumarin products (a core prevalent in natural products and molecules of medicinal interest) containing three contiguous stereocentres. 相似文献
20.
Yusaku Honjo Dr. Yu Shibata Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9427-9432
It has been established that an electron-deficient cyclopentadienyl rhodium(III) (CpERhIII) complex catalyzes the oxidative and decarboxylative [2+1+2+1] cycloaddition of benzoic acids with diynes through C≡C triple bond cleavage, leading to fused naphthalenes. This cyclotrimerization is initiated by directed ortho C−H bond cleavage of a benzoic acid, and the subsequent regioselective alkyne insertion and decarboxylation produce a five-membered rhodacycle. The electron-deficient nature of the CpERhIII complex promotes reductive elimination giving a cyclobutadiene–rhodium(I) complex rather than the second intermolecular alkyne insertion. The oxidative addition of the thus generated cyclobutadiene to rhodium(I) (formal C≡C triple bond cleavage) followed by the second intramolecular alkyne insertion and reductive elimination give the corresponding [2+1+2+1] cycloaddition product. The synthetic utility of the present [2+1+2+1] cycloaddition was demonstrated in the facile synthesis of a donor–acceptor [5]helicene and a hemi-hexabenzocoronene by a combination with the chemoselective Scholl reaction. 相似文献