Basicity of Some Mono- and Bicyclic Enamines and Tricyclenamines

Cook, A. Gilbert; Absi, Michelle L.; Bowden, Virginia K.

doi:10.1021/jo00115a037

Cited by 21 publications

(19 citation statements)

References 2 publications

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“…2.5 units more basic than the corresponding morpholine-containing enamines. 13 Reduction of a 1 : 1 mixture of 1p and 1m gave a 4.0 : 1 ratio of products (Table 2). A larger rate difference in protonation rates would have been expected for a difference of 2.5 p K a units.…”

Section: Resultsmentioning

confidence: 99%

SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

2017

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Samarium diiodide in the presence of water and THF (SmI2(H2O)n) has in recent years become a versatile and useful reagent, mainly for reducing carbonyl-type substrates. This work reports the reduction of several enamines by SmI2(H2O)n. Mechanistic experiments implicate a concerted proton-coupled electron transfer (PCET) pathway, based on various evidence against initial outer-sphere electron transfer, proton transfer or substrate coordination. A thermochemical analysis indicates that the C-H bond formed in the rate determining step has a bond dissociation free energy (BDFE) of ~32 kcal mol−1. The O–H BDFE of the samarium aquo ion is estimated to be 26 kcal mol−1, which is among the weakest known X–H bonds of stable reagents. Thus SmI2(H2O)n should be able to form very weak C-H bonds. The reduction of these highly electron rich substrates by SmI2(H2O)n shows that this reagent is a very strong hydrogen atom donor as well as an outer sphere reductant.

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Section: Resultsmentioning

confidence: 99%

SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

2017

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“…[38,39] As eries of acids was therefore tested as additives with the goal of finding ap robable relationship between pK a of the acid and the outcome of the a-alkylation of aldehydes. Careful analysis of the data included in Table 3led to interesting observations and generalizations.…”

Section: Models Tudiesmentioning

confidence: 99%

Photocatalytic Reaction of Diazo Compounds with Aldehydes

2016

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“…The six-membered ring enaminoketones are only slightly stronger bases than the saturated amines, whereas five-and-seven membered rings are much stronger bases than saturated amines. This has been attributed to a large steric strain present in six-membered enaminoketones [5].β-Aminoenones or enaminoketones can exist in four conformations owing to restricted rotations around the C=C double and C-C=O single bonds [3]. Enaminones with primary or secondary amino groups can exist in both Z-and E-forms.…”

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confidence: 99%

Recent development in preparation reactivity and biological activity of enaminoketones and enaminothiones and their utilization to prepare heterocyclic compounds

Negri

Kascheres

2004

Journal of Heterocyclic Chem

179

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Enaminoketones and esters are gaining increased interest, particularly cyclic-β-enaminoesters, which are known as important intermediates for the synthesis of heterocycles and natural products, because the enantioselective preparation of highly functionalized compounds is of central importance in synthetic chemistry. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. Enaminoketones and enaminonitriles have proven to be versatile building blocks for the synthesis of various heterocycles such as pyridine, pyrimidine and pyrrole derivatives. Enaminones systems have "enone" character, and may act as acceptors in both 1,2 and 1,4-additions. In this way the enaminone serves as a scaffold for annulation, and can gain access to systems such as pyrroles indolizidines, quinolizidines and perhydroindoles, all of which are common motifs in alkaloid structures. Enaminones are frequently employed as building blocks for the preparation of a variety of bicyclic compounds of biological interest and have been recently recognized as potential anticonvulsant compounds. Since a large number of developments in the use of enaminones in heterocyclic synthesis have occurred, a review of the recent developments in the synthetic approaches, covering the literature since 1995 until 2004, to these interesting molecules and their useful chemical transformations and biological activity can be considered of considerable value.J. Heterocyclic Chem., 41, 461 (2004).Enaminoketones. Introduction.The term enaminone was introduced by Greenhill to define the enamine of a 1,3-diketone, β-ketoester or similar 1,3-difunctional reagents, and is used to indicate any compound containing the conjugated system N-C=C-C=O [1]. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. The chemistry of the enaminocarbonyl group 1 is potentially an area of considerable scope when one considers that there are present in this moiety, three nucleophilic sites (a, c and e) and two electrophilic sites (b and d) [2][3][4] (Figure 1).Theorically, primary and secondary acyclic enaminones can exist in three tautomeric forms: ketamino form, iminoenol form and oxoimino form [1][2][3]. There is also evidence that cyclic enaminones exist primarily in the enaminoketo form. A study of cyclic enaminoketones shows that these compounds have a significant steric fator in the six-membered ring. The six-membered ring enaminoketones are only slightly stronger bases than the saturated amines, whereas five-and-seven membered rings are much stronger bases than saturated amines. This has been attributed to a large steric strain present in six-membered enaminoketones [5].β-Aminoenones or enaminoketones can exist in four conformations owing to restricted rotations around the C=C double and C-C=O single bonds [3]. Enaminones with primary or secondary amino groups can exist in both Z-and E-forms. If there is a...

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Basicity of Some Mono- and Bicyclic Enamines and Tricyclenamines

Cited by 21 publications

References 2 publications

SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

Photocatalytic Reaction of Diazo Compounds with Aldehydes

Recent development in preparation reactivity and biological activity of enaminoketones and enaminothiones and their utilization to prepare heterocyclic compounds

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Basicity of Some Mono- and Bicyclic Enamines and Tricyclenamines

Cited by 21 publications

References 2 publications

SmI2(H2O)n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

SmI2(H2O)n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

Photocatalytic Reaction of Diazo Compounds with Aldehydes

Recent development in preparation reactivity and biological activity of enaminoketones and enaminothiones and their utilization to prepare heterocyclic compounds

Contact Info

Product

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SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer

SmI₂(H₂O)_n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer