Aromatic imine stereochemistry as studied by 13C and 1H NMR of 15N‐enriched materials

Buchanan, G. W.; Dawson, Brian

doi:10.1002/mrc.1270130416

Cited by 38 publications

(4 citation statements)

References 23 publications

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“…The results presented show unequivocally that the C-15N coupling constants over one bond in compounds containing an azo group are configurationspecific and, hence, very important for assignment purposes. 13…”

Section: Discussionmentioning

confidence: 99%

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Fanghänel¹,

Radeglia²

1983

Org. Magn. Reson.

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The "C NMR spectra of singly 'SN-labelled Z/E isomers of azo and diazo compounds were recorded. The J( C N) coupling constants are strongly dependent on the geometrical configuration of the azo group, the relative position of the lone pair of electrons at the non-coupling azo nitrogen atom having a decisive influence. l3 15 INTRODUcIlONLittle experimental material is available in the literature on the influence of the geometrical configuration around an N=N double bond on the 'sN-'3C coupling conditions over one bond (see Fig. 1).Schwotzer et al.' found a relatively large difference between the 'J(13C1'N) values of the Z and E isomers in azoxybenzenes, whereas this difference is not very distinct in Z/E isomers of azimines. Recently, coupling constants of the ZIE isomeric azobenzenes and benzo[c]cinnoline were published,2 which also prove the specific influence of the configuration on the coupling conditions. Our own investigations show, however, that the assignments reported in Ref. In a previous study,3 we were also able to show that the I3C--l5N coupling constants of Z / E isomeric benzthiazoline-2-ylidenearyltriazenes and triazenium salts are significantly dependent on the geometrical configuration. To improve the understanding of this dependence, we have carried out a comparative study of the l3C-I5N coupling constants over one bond in Z -and E-azobenzenes 1, benzo[c]cinnoline (Z), diazocyanides 3, triazenes 4, and triazenium salts 5 with Z and E configurations, also including the literature values of azoxybenzenes 6.'

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Section: Discussionmentioning

confidence: 99%

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Fanghänel¹,

Radeglia²

1983

Org. Magn. Reson.

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“…3 Previous observations in our have show that 13C-15N spin couplings in anilines are subject to significant electronic and steric influences. It was therefore of interest to investigate compounds having substituents in the aniline ring and, in particular, at the ortho position where possible steric effects on the molecular conformation could be examined.…”

Section: Introductionmentioning

confidence: 86%

Substituent effects on ¹³C–¹⁵N spin couplings and ¹³C chemical shifts in benzylideneanilines

Axenrod

Huang

Wieder

et al. 1986

Magnetic Reson in Chemistry

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“…The explanation advanced by Dodsworth et al (2) to account for the preferred formation of cis isomers in the acyclic series will not serve for the cyclic systems; an alternative explanation is offered below. Acyclic imines exist almost exclusively in the E configuration (22,23) while the cyclic imines studied here can exist only in a Z configuration. Isomerism is possible in the acyclic system in the presence of a nucleophile and some Z isomer may be present in the reaction system and react as such.…”

mentioning

confidence: 86%

Condensation of cyclic and acyclic imines with phthalide anions. Synthesis of protoberberines and substituted 3,4-dihydro-2-methyl-1(2H)-isoquinolones

Marsden¹,

MacLean²

1984

Can. J. Chem.

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, 1392 (1984). 3,4-Dihydroisoquinolines react with anions derived from phthalides and 3-methylphthalides in tetrahydrofuran yielding 13-hydroxy-8-oxotetrahydroprotoberberines and 13-hydroxy-l3-methyl-8-oxotetrahydroprotoberberines, respectively. Only one of two possible diastereomers is formed. The lactams may be reduced to the corresponding protoberberines with lithium aluminium hydride. The reaction of the acyclic imine, 3,4-dimethoxybenzylidenemethylamine, with anions derived from phthalide, 3-phenylphthalide, and 5.6-dimethoxyphthalide, has been investigated. In all cases separable mixtures of diastereomeric substituted 3,4-dihydro-l(2H)-isoquinolones were formed. RICHARD 1392 (1984). Les dihydro-3,4 isoquinolCines, dans le titrahydrofuranne, rCagissent avec les anions provenant des phthalides et des mCthyl-3 phthalides pour conduire respectivement aux hydroxy-13 0x0-8 tCtrahydroprotoberbCrines et aux hydroxy-1 3 methyl-13 0x0-8 tCtrahydroprotoberbCrines. I1 ne se forme qu'un seul des deux diastCrCoisomkres. On peut rCduire les lactames en protoberbkrines correspondantes en faisant appel ii I'hydrure double de lithium et d'aluminium. On a CtudiC la rCaction de I'imine acyclique, dimCthoxy-3,4 benzylidknemCthylamine, avec les anions provenant du phthalide, du phknyl-3 phthalide et du dimCthoxy-5,6 phthalide. Dans tous les cas, il se forme des mClanges, que I'on peut sCparer, des diastCrCoisom2res des dihydro-3,4 (2H)-isoquinolones-I substituCes.[Traduit par le journal] IThe reaction of imines with phthalide anions derived from phthalides and lithium diisopropylamide (LDA) was reported in a preliminary communication in 1980 by Dodsworth et al.(1). A more complete account of their work leading to the formation of various diarylisoquinolones has recently appeared (2). In the interim we reported our initial studies on the reaction of phthalide anions with 3,4-dihydroisoquinolines, a reaction that leads in one step to the protoberberine ring system (3). Here we give a full account of our initial work, and its extension to the synthesis of 13-methylprotoberberines. We also report the preparation of several 2-methyl-3-phenyl-4-hydroxy-3,4-dihydro-1 (2H)-isoquinolones and a pair of 2-methyl-3,4-diphenyl-4-hydroxy-3,4-dihydro-1 (2H)-isoquinolones. Dodsworth et al. (2) showed that the anions of phthalide ( l a ) and 5,6-dimethoxyphthalide (lb) react with a variety of diary1 imines 2 to form 3,4-dihydro-l(2H)-isoquinolones substituted at C-2 and C-3 by the aryl groups present in imine 2 and at C-4 by an OH group. (The generation of two new chiral centres leads to the formation of racemic diastereomers as shown in Scheme 1 .) This reaction very likely proceeds by initial attack of phthalide anion at the carbon atom of the carbon-nitrogen double bond with transfer of charge to nitrogen. The negatively charged nitrogen then attacks the phthalide carbonyl carbon to form a tetrahedral intermediate which opens to form the isoquinolone. Dodsworth et al. found that the formation of the cis isomer 3 was favored over the tran...

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Aromatic imine stereochemistry as studied by ¹³C and ¹H NMR of ¹⁵N‐enriched materials

Cited by 38 publications

References 23 publications

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Substituent effects on ¹³C–¹⁵N spin couplings and ¹³C chemical shifts in benzylideneanilines

Condensation of cyclic and acyclic imines with phthalide anions. Synthesis of protoberberines and substituted 3,4-dihydro-2-methyl-1(2H)-isoquinolones

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Aromatic imine stereochemistry as studied by 13C and 1H NMR of 15N‐enriched materials

Cited by 38 publications

References 23 publications

Influence of the Z/E configuration on the 13C15N coupling conditions 1J(13C15N) in aromatic azo and diazo compounds

Influence of the Z/E configuration on the 13C15N coupling conditions 1J(13C15N) in aromatic azo and diazo compounds

Substituent effects on 13C–15N spin couplings and 13C chemical shifts in benzylideneanilines

Condensation of cyclic and acyclic imines with phthalide anions. Synthesis of protoberberines and substituted 3,4-dihydro-2-methyl-1(2H)-isoquinolones

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Aromatic imine stereochemistry as studied by ¹³C and ¹H NMR of ¹⁵N‐enriched materials

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Influence of the Z/E configuration on the ¹³C¹⁵N coupling conditions ¹J(¹³C¹⁵N) in aromatic azo and diazo compounds

Substituent effects on ¹³C–¹⁵N spin couplings and ¹³C chemical shifts in benzylideneanilines