Untersuchungen an derivaten des 1,3,5-triazepins

Stüwe, A.; Mattheus, A; Heınze, Jürgen; Baumgärtel, H.

doi:10.1016/s0040-4020(01)93140-0

Cited by 4 publications

(1 citation statement)

References 14 publications

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“…Addition of 1,8-diazabicyclo[5. 4.O]undec-7-ene (DBU) to a suspension or solution of the amidine 2 in a large excess of an aldehyde or ketone at room temperature gave an immediate exothermic reaction with dissolution of compound 2 and the precipitation of a solid. In the case of aldehydes these products 3 are yellow-orange, while with acetone it is off-white.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 4-substituted 8-amino-4,5-dihydro-3H-pyrrolo[3,4-f]-1,3,5-triazepin-6-ones and 5-amino-2-aryl-4-(1-aryl-5-alkylideneaminoimidazol-4-yl)1,3-oxazoles

Alves¹,

Ai-Duaij²,

Booth³

et al. 1994

J. Chem. Soc., Perkin Trans. 1

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Section: Resultsmentioning

confidence: 99%

Synthesis of 4-substituted 8-amino-4,5-dihydro-3H-pyrrolo[3,4-f]-1,3,5-triazepin-6-ones and 5-amino-2-aryl-4-(1-aryl-5-alkylideneaminoimidazol-4-yl)1,3-oxazoles

Alves¹,

Ai-Duaij²,

Booth³

et al. 1994

J. Chem. Soc., Perkin Trans. 1

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Darstellung und Struktur von 1‐Oxa‐3,5‐diaza‐1,3,5‐hexatrienen. Die 1‐Oxa‐3,5‐diaza‐1,3,5‐hexatrien/2H‐1,3,5‐Oxadiazin‐Tautomerie

1993

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Key Words: l-Oxa-3,5-diaza-1,3,5-hexatrienes / 2H-1,3,5-0xadiazines / l-Oxa-3,5-diaza-l,3,5-hexatriene -2H-1,3,5-0xa-diazine tautomerism / Ring-chain tautomerism / Calculations, ab initio Synthesis and Structures of l-Oxa-3.5-diaza-l.3,5-hexatrienes. The l-Oxa-3,5-diaza-1.3,5-hexatriene/2H-1.3.5-Oxadiazine TautomerismReaction of N-lithio-or N-trimethylsilyl-substituted imines 1 with N-acylimidic acid derivatives 2 provides l-oxa-3,5-diaza-1,3,5-hexatrienes 3 in fair to good yields. Depending on the substitution pattern, the acyclic compounds 3 form an equilibrium with their cyclic tautomers, e.g. 2H-1,3,5-oxadiazines 4.Aromatic substituents at C-6 favor the acyclic form 3, whereas aliphatic groups (e.g. tert-butyl) lead to the exclusive formation of the ring tautomer 4. For a typical example (3d/4d) the free enthalpy of activation for the ring/chain tautomerism was determined to be ca. 12.5 kcal/mol. Detailed spectroscopic data ('H-, 13C-NMR, IR, UV) for both tautomers are given. The XRay analysis of the acyclic compound 3a shows a central C = N bond with Z configuration and with s-gauche conformations of the adjacent C = O and C = N systems. According to quantum mechanical ab initio calculations (MP2/6-31G'//6-31G') for the C3H4N20 model compounds, the ring tautomer 6 is by ca. 6 kcal/mol lower in energy than the acyclic forms ?. Within the series of open-chain tautomers 7, gauche forms are lower in energy than s-trans conformers, indicating that amide resonance is more important for these systems than polyene delocalization. s-cis Forms were found to be transition states. The acyclic conformers 7 are rather flexible; barriers of rotation for both C -N bonds are calculated to 4 -5 kcal/mol only (RHF/ 3-21G//3-21G).In den letzten Jahren ist die Bedeutung von Heterobutadienen in organischen Synthesen, besonders in Cycloadditionen"], stark gewachsen. Dies regte uns dazu an, die Reaktivitat dieser Verbindungen auf der Grundlage ihrer elektronischen und strukturellen Eigenschaften zu interpretieren. Die von uns in diesem Zusammenhang an 1-0xa-3-azabutadienen[*] und 1,3-Dia~abutadienen[~] durchgefuhrten Untersuchungen zeigten die interessante Stereochemie dieser Verbindungen auf, wobei niedrige Barrieren fur Rotationen um die C -N-Einfachbindungen dieser Amidin-bzw. Carbonsaureamid-verwandten Verbindungen hervorzuheben sind. Ein wesentlicher strukturbestimmender Faktor ist dabei die in Konkurenz zur n/n-Konjugation auftretende n/ 7c-Wechselwirkung, die zur Begunstigung von verdrillten Strukturen fuhrt. Diese Ergebnisse motivierten uns zu einer eingehenden Untersuchung der Strukturchemie verlangerter azavinyloger Heteroen-Systeme. In diesem Beitrag werden die strukturellen Eigenschaften der kaum bekannten 1-Oxa-3,5-diaza-l,3,5-hexatrieneL4I 3 untersucht. Neben den elektronischen Wechselwirkungen werden besonders die Auswirkungen der additiven Verknupfung der molekularen Bindungsdipole im C = N -C = N -C = 0-System auf die Molekulstruktur berucksichtigt. In dieser Atomanordnung sind Molekule rnit ungewohnlich groBen Dip...

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