Enamines—XXXIX : Enamines from cyclopropylketones

The enamines from cyclopropyl-methyl-, -ethyl- and -cyclopentylketone have been prepared by reaction of the ketone with a secondary amine and TiCl₄. Their vinylcyclopropane structure has been demonstrated by NMR. The reaction of dicyclopropylketone, cyclopropylphenylketone or cyclopropyl-α-thienylketone with secondary amines and TiCl₄ afforded homoallylic rearrangement products, namely 1-cyclopropyl-, 1-phenyl- and 1-(α-thienyl)-1,4-diamino-1-butene, respectively.     

Cycloaddition Reactions of Enamines

This review includes information for around two last decades on cycloaddition reactions of enamines with various agents in order to build carbo- and heterocycles. In addition, the review presents organo-catalytic reactions in which enamines are intermediate products generated in situ. This review covers the synthesis of four, five, six and eight-membered carbocyclic compounds, as well as heterocycles as pyrroles, pyridines, etc.     

Enamines. V

The two-electron electrical reduction of 4-hydroxymethylene-3-oxocaprolactam in aqueous solutions at pH < 3 proceeds reversibly to give the corresponding enediol, from which 4-formyl-3-hydroxycaprolactam (the principal pathway) and 4-hydroxymethylene-3-oxocaprolactam are formed by a protropic shift. An increase in the pH of the medium leads to acceleration of the subsequent chemical steps and determines the irreversibility of the reduction at pH > 4.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 486–490, April, 1977.     

二甲基甲酰胺催化的烯胺还原反应

用路易斯碱二甲基甲酰胺(DMF)催化三氯氢硅(HSiCl3)还原烯胺合成对应的胺,最佳反应条件为:烯胺0.1 mmol, DMF 0.5 eq., HSiCl3 4.0 eq., DCM 1 mL,于0 ℃反应12 h,胺的收率在93%以上.     

The Phosphorylated Enamines

Abstract

The primary phosphorylated enamines were obtained by aminomethylenation of the phosphorus-containing CH-acids with bis-silylformamide.     

Structural Studies of Crystalline Enamines

Crystal structure analyses of five crystalline enamines together with recently published structural data for two other enamines reveal varying degree of pyramidality at the enamine nitrogen atom. The pyramidality appears to be most pronounced in enamines from piperidine and morpholine, less so in enamines derived from prolinoid amines. A pyrolidine enamine obtained from a derivative of cyclohexane-1,4-dione seems to have a virtually planar enamine group. The implications of these findings for current stereochemical problems in enamine chemistry are discussed.     

Enamines of the 5-nitrofuran series

New enamines and quaternary salts of 5-nitro-2-vinylfuran were obtained by reaction of 1-bromo-2-(5-nitro-2-furyl) ethylene with secondary and tertiary amines. The trans conformation of the investigated compounds was established by means of their IR, UV, and PMR spectra and dipole moments.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 311–314, March, 1978.     

Unusual Reaction of Diazo Compounds with Enamines

Transition metal catalyzed decomposition of diazo compounds and consequent transformations constitute various synthetic useful reactions in the past decades. The catalytic addition of diazo compounds to olefins generally provides cyclopropanes in high yield. However the reaction of electron-rich enamines with diazo compounds gave variable results. Wenkert et al. reported the reaction of enamines with ethyl diazoacetae (EDA) in the presence of cuprous chloride or silver oxide unexpectedly gave…     

Chemoselective Silylative Reduction of Conjugated Nitriles under Metal‐Free Catalytic Conditions: β‐Silyl Amines and Enamines

The B(C₆F₅)₃‐catalyzed silylative reduction of conjugated nitriles has been developed to afford synthetically valuable β‐silyl amines. The reaction is chemoselective and proceeds under mild conditions. Mechanistic elucidation indicates that it proceeds by rapid double hydrosilylation of the conjugated nitrile to an enamine intermediate which is subsequently reduced to the β‐silyl amine, thus forming a new C(sp³)? Si bond. Based on this mechanistic understanding, a preparative route to enamines was also established using bulky silanes.     

Enamines organostanniques chirales: Synthese et structure

Spectroscopic studies (¹H and ¹¹⁹Sn NMR, IR) showed that aldiminoalcohols reacted with bis(dimethylamino)dibutyltin via a transient secondary enamine. This compound was acidic enough to cleave the remaining SnN bond leading to oligomeric organotin enamines (5-coordinated tin atom) probably of E configuration. Several oligomeric species were in equilibrium and slight modification of the experimental conditions (+20 to +50°C) affected these equilibriums significantly.     

共轭烯烃的共轭极化势

Based on the conjugated polarization theory,it is expressed as the conjugated polarizability potential （CPP）that the discrepancy between the average electrostatic energy of dipolar state and the electrostatic energy of non-polar state in the conjugated polarizability procedure for the conjugated alkenes. The correlation between CPP and the energy of ultraviolet absorption maximum,and the correlation between the energy of frontier molecular orbital obtained by ab initio calculation of quantum chemistry and the energy of ultraviolet absorption maximum have been carried out for the conjugated alkenes. Both correlation equations show a similar estimated precision. Further, the contribution of alkyl polarizability effect to the stability of dipolar state for the alkyl substituted alkenes with the effective polarizability effect index（PEI（ef））was quantified. Relating the above two parameters CPP and PEI（ef）to the energy of ultraviolet absorption maximum of the substituted alkenes in a two-parameter expression with a good prediction ability was obtained:v=1.1746+5.0187CPP-0.43204PEI （ef）,R=0.9995,s=0.0403,F=10853.28,n=23. The investigated results also indicate that it is less effective to reduce the energy of ultraviolet absorption maximum by means of increasing the alkyl substituent groups than lengthening the conjugated backbone chain in the conjugated alkenes.     

Michael-Type Addition Reactions of Some Enamines to Arylidenepyrazolones

The reaction of the arylidenepyrazolones (1_b-d) with l-morpholinocyclohexene (E₂) in refluxing acetonitrile leads to the less substituted alkylated enamines 3_b-d. On the other hand, the more substituted alkylated enamines 2_a-d are formed when 1_a-d react under the same conditions with l-piperidinocyclohexene (E₁). The nature of the enamine is crucial. Nucleophilic attack of the enamine on the α, β-unsaturated carbonyl system of 1 gives rise to a zwitterionic intermediate which through α -proton loss leads to different Michael-type adducts depending on the enamine.     

Enamines from terminal epoxides and hindered lithium amides

A new reactivity mode of lithium amides with epoxides leads to hindered enamines. The reaction of some of these enamines with unactivated primary and secondary alkyl halides is described, which expands the range of electrophiles that one can use in the synthesis of mono-alkylated aldehydes.     

C-Thiocarbamoylation of Electron-Rich Heterocycles and Enamines with Amidophosphonium Isothiocyanates

Amidophosphonium isothiocyanates thiocarbamoylate a series of electron-rich heterocycles and enamines at the nucleophilic carbon atom to form phosphazothiocarbonyl compounds. From the most active heterocycles, bis(phosphazothiocarbonyl) derivatives can be obtained.