Tris(phenylimino)-1,3-diphenyl-1,2,3-propantrione:  A Model Compound Implicating a Nonhelical Structure for Poly((<i>N</i>-phenylimino)methylene)

Spencer, Lynne; Kim, Misoo; Euler, William B.; Rosen, William

doi:10.1021/ja970880q

Cited by 14 publications

(8 citation statements)

References 20 publications

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“…Examination of this mixture by 1 H-decoupled 15 N NMR, after equilibrium was reached, indicated that additional resonance bands had appeared in relative amounts of 12% and 4% with respect to the starting triimine resonance bands. The 12% resonances appeared at δ = 333.6 and 359.1 ppm (vs 15 NH 3 ) as singlets while the 4% resonances appeared at δ = 350.3 and 355.6 ppm as doublets having 3 J N - N = 2.7 Hz . We attributed the 12% resonances to hydrolytically derived IIa while the 4% resonance doublets were attributed to IIb (see Scheme ) and we surmised that these 1-keto-2,3-diiminopropane derivatives were an equilibrating 3:1 mixture of atropisomers.…”

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confidence: 81%

“…Whether the underlying σ-Y-shaped atomic frameworks are capable of supporting fully conjugated π-electron delocalized and stabilized systems has generated considerable debate . Recently we have shown that unconstrained σ-Y-frameworks, supporting cross-conjugated π-systems, have a skewed geometry . In this Letter we report additional examples of unconstrained, cross-conjugated systems that are capable of sampling Y-delocalization.…”

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confidence: 84%

“…The 12% resonances appeared at δ ) 333.6 and 359.1 ppm (vs 15 NH 3 ) as singlets while the 4% resonances appeared at δ ) 350.3 and 355.6 ppm as doublets having 3 J N-N ) 2.7 Hz. 5 We attributed the 12% resonances to hydrolytically derived IIa while the 4% resonance doublets were attributed to IIb (see Scheme 1) and we surmised that these 1-keto-2,3-diiminopropane derivatives were an equilibrating 3:1 mixture of atropisomers. We assumed further that the conformational and configurational structures shown in Scheme 1 for IIa and IIb were most reasonable on the basis of our previous experience with these types of cross-conjugated systems.…”

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confidence: 87%

“…4 Recently we have shown that unconstrained σ-Yframeworks, supporting cross-conjugated π-systems, have a skewed geometry. 5 In this Letter we report additional examples of unconstrained, cross-conjugated systems that are capable of sampling Y-delocalization. Instead of π-delocalized planarity, the most obvious conformational hallmark in our systems is mobility that equilibrates energetically separable configurations.…”

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confidence: 95%

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Configurational and Conformational Mobility in a Cross-Conjugated Derivative of 1,3-Diketo-2-iminopropane

Song¹,

Spencer²,

Euler³

et al. 1999

Org. Lett.

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Mobility of configuration and conformation in the “push−pull” cross-conjugated derivative 1,3-diphenyl-2-(p-dimethylaminophenyl)iminopropane-1,3-dione has been investigated by NMR. The energetics of the thermal process that interconnects the syn- and anti-configurations of the imino group with the atropisomeric conformations of the skewed benzoyl groups are defined. It is proposed that a symmetric Y-delocalized transition state thermally interconnects the inversion of the imino configurations with the mobile interchange of the skewed benzoyl conformations. This connection is observable through a unique NMR window.

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confidence: 81%

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confidence: 84%

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confidence: 87%

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confidence: 95%

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Configurational and Conformational Mobility in a Cross-Conjugated Derivative of 1,3-Diketo-2-iminopropane

Song¹,

Spencer²,

Euler³

et al. 1999

Org. Lett.

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“…In an attempt to rectify the dearth of information having physico-chemical signiÐ-cance to the problem of helicity in the vic-polyimine family, we have initiated a program of synthesis and NMR analysis of these interesting molecules. 7 The study reported in this paper was initiated to Ðnd a better description of the conformations of sterically unhindered PIMs. The target polymer of our investiga- tion was poly(N-phenyliminomethylene) (/-PIM).…”

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confidence: 99%

Complete solution NMR analysis of three oligoimine model compounds

et al. 1998

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Squaramide‐Catalyzed Synthesis of Enantioenriched Spirocyclic Oxindoles via Ketimine Intermediates with Multiple Active Sites

et al. 2015

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An ew method for the construction of five-membered spirocyclic oxindoles is based on aM ichael-Mannich cascade reaction of ak etimine intermediated catalyzedb y abifunctional quinine-derived squaramide.The desired products were obtained in excellent yields (up to 94 %) and stereoselectivities (up to > 20:1 d.r., > 99 %e e). As caled-up variant also proceeded smoothly showing that the one-pot reaction might find application in the synthesis of bioactivecompound libraries.The spirocyclic oxindole architecture is prevalent in both natural products and synthetic bioactive molecules (Figure 1). [1] In particular, enantiopure five-membered spirocyclic oxindoles have attracted tremendous attention owing to their diverse bioactivities and structural complexity.T he key challenge for the construction of such structures lies in the formation of multiple stereocenters,p articularly for those containing two adjacent quaternary centers.T herefore,n ew strategies for the synthesis of such spirocyclic oxindoles [2] with high levels of efficiency and selectivity from readily available starting materials are always in great demand.In the past few years,elegant advances have been made in the development of enantioselective syntheses of five-membered spirocyclic oxindoles.[3] In 2007, Tr ost [4] and co-workers disclosed ap alladium-catalyzed [3+ +2] cycloaddition for the assembly of such compounds.A side from transition-metal catalysis,o rganocatalytic cascade reactions provide an alternative powerful strategy for the preparation of spirocyclic oxindoles.A fter [3+ +2] cycloadditions catalyzed by chiral tertiary phosphines [5] or amines [6] had been reported, hydrogen bond donor catalyzed cascade reactions, [7] MichaelMichael reactions promoted by primary [8] or secondary amines, [9] NHC-catalyzed processes, [10] as well as alkylations mediated by phase transfer catalysts (PTCs) [11] were developed. More recently,s ynergistic catalysis [12] and CÀHb ond oxygenation [13] were also applied to the asymmetric construction of five-membered spirocyclico xindoles.Inspired by our ongoing interest in the development of reactions towards spirocyclico xindoles [14] and previous work on nitrosoarenes, [15] we hypothesized that the addition of b-dicarbonyl compounds to nitrosoarenes followed by aMichael-Mannich sequence in the presence of abifunctional catalyst would be an appropriate strategy to prepare enantioenriched spirocyclico xindoles (Scheme 1d). As an interesting electrophile,n itrosobenzene can react with ketones/ aldehydes to form either the a-aminooxylation [16] or the a-oxyamination products [17] (Scheme 1a). However,very few methods for the addition of b-dicarbonyl compounds [18] to nitrosoarenes to generate a-imino-b-dicarbonyl compounds have been reported thus far,a nd they all suffer from low yields (Scheme 1b). These products are very useful synthons that bear multiple nucleophilic and electrophilic sites.T othe best of our knowledge,t he application of these novel ketimines in asymmetric synthesis has not been repor...

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Tris(phenylimino)-1,3-diphenyl-1,2,3-propantrione: A Model Compound Implicating a Nonhelical Structure for Poly((N-phenylimino)methylene)

Cited by 14 publications

References 20 publications

Configurational and Conformational Mobility in a Cross-Conjugated Derivative of 1,3-Diketo-2-iminopropane

Configurational and Conformational Mobility in a Cross-Conjugated Derivative of 1,3-Diketo-2-iminopropane

Complete solution NMR analysis of three oligoimine model compounds

Squaramide‐Catalyzed Synthesis of Enantioenriched Spirocyclic Oxindoles via Ketimine Intermediates with Multiple Active Sites

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