The Photochemistry of Nitrogen-Containing Heterocycles

Reid, S. T.

doi:10.1016/s0065-2725(08)60029-x

Cited by 14 publications

(3 citation statements)

References 378 publications

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“…13,14 There are numerous nitrogen-containing heterocyclic compounds among those systems that exhibit interesting photochemical behaviour. 15,16 Among them, Schiff bases with highly conjugated systems with aromatic substituents bonded to an aliphatic backbone are associated with photochemicallyinduced biological processes. 17 Their properties of chemical and biological signicance [18][19][20] can be attributed to the presence of the double bond (N]C or N]N), oen acting as a linkage between aromatic systems.…”

Section: Introductionmentioning

confidence: 99%

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

2022

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Section: Introductionmentioning

confidence: 99%

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

2022

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“…[10] More particularly, the selective modification of nucleosides is a challenge in the quest for the development of medicinal agents effective for the treatment of cancer and viral infections, such as herpes and AIDS. [11] Part of this effort has involved the utilization of the 5,6-double bond for synthetic elaboration by means of inter-and intramolecular electrophilic additions [12] or cycloaddition processes, such as 6p-electrocyclizations, [22] cycloadditions, [32] photoadditions, [13] and [42] Diels ± Alder reactions with appropriately functionalized pyrimidones. [14] In this paper, we wish to report the scope and limitations of our studies which are directed towards the chemo-, regio-, and stereoselective participation of pyrimidine derivatives in cobalt-mediated [222] cycloaddition reactions as a new synthetic entry to modified nucleosides.…”

Section: Introductionmentioning

confidence: 99%

“…Direct acylation of uracil (5: R 1 R 2 H) with 4-pentynoyl chloride [23] following a reported procedure afforded 6 f in 60 % yield. [13] The cyano derivatives 6 g (n 1) and 6 h (n 1) have been prepared in 60 % and 66 % yields, respectively, by Michael addition of the corresponding pyrimidinediones to acrylonitrile, [24] while 6 i (n 2, R 1 R 2 H) was obtained in 37 % yield by direct alkylation of 5 (R 1 COPh, R 2 H) with 4-chlorobutyronitrile by the use of K 2 CO 3 in THF and concomitant saponification of the benzoyl protecting group at N3. Similarly, alkylation of N-acetylcytosine (3 a) gave the desired 1N-(1pentyne) derivative 7 in 88 % yield (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Cobalt-Mediated [2+2+2] Cycloadditions of Pyrimidine Derivatives to Alkynes

1999

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The scope and limitations of the cobalt-mediated [222] cycloaddition of pyrimidine derivatives to alkynes has been investigated. The 5,6-double bond of these heterocyclic nuclei has been found to participate in an entirely intermolecular fashion to generate chemo-and stereoselectively novel, fused and substituted 5,6-dihydropyrimidine cobalt complexes, which upon oxidative demetallation liberate the correspond-ing new heterocyclic ligand. On the other hand, 1-alkynyl pyrimidines have been found to be suitable partners in the cocyclization with disubstituted alkynes, such as bis(trimethylsilyl)acetylene (BTMSA) or dimethyl 2-butyn-1,4-dioate (DMAD), to allow the direct prep-aration of hitherto unknown dihydropyrido[3,2-ij]quinazoline cobalt complexes. Effects of the substitution on the pyrimidine nucleus, the cocyclization partner, the complex auxiliary, and the reaction conditions were examined, and in some cases competing pathways that lead to [CpCo(cyclobutadienes)], cyclopentadienone complexes, and compounds that arise from a C À H activation-type reaction were observed.

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Chemo‐ und stereoselektive Cobalt‐vermittelte [2+2+2]‐Cycloaddition von Alkinen mit Uracil‐Derivaten: Ein neuer Syntheseweg zu modifizierten Nucleosiden

Boese¹,

Rodríguez

Vollhardt

1991

Angewandte Chemie

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Ebenso rufen entschirmende Effekte des jetzt ,,vollstandigen" n-Elektronensystems der Benzoleinheit in 4, wie nach Memorvs Gleichung['I leicht zu berechnen. Anderungen um ca. Ah = 0.05 hervor und sind damit vernachlassigbar. Wir gehen daher in 4 von einem paratropen Ringstrom aus. Dies wiirde die Tieffeldverschiebung der Signale (Ah = I ) der inneren Methylprotonen in 4 relativ zu 5 erklaren, da die chemische Verschiebung der entsprechenden Protonen der bekannten['I. geometrisch sehr ahnlichen paratropen (t2lAnnulene 8 bei 6 = 2.58 liegt. Zudem kann Giinthers Q- Wert"] fur die Benzoleinheit in 2 zu 0.99 und 1.02 berechnet werden. Diese unter dem Grenzwert von 1.04 liegenden Werte weisen somit eindeutig auf eine Paratropie (ein delokalisiertes 4n-n-Elektronensystem) des Makrocyclus in 4 hin. Dies laOt sich rnit einer Riickbindung des Eisens in die Annuleneinheit deuten, in der dem n-Elektronensystem formal zwei zusitzliche Elektronen zur Verfiigung gestellt werden. Das resultierende 16 n-Elektronensystem sollte paratrop sein. In der Tat sind die Ringprotonen der Benzoleinheit in 4 (H7lo), im Vergleich zum Benzol selbst abgeschirmt, was bei einem atropen (bindungsfixierten) Makrocyclus nicht zu erwarten gewesen ware. Ebenso sind die 'H-'H-Kopplungskonstanten der Benzoleinheit fast identisch und nicht stark alternierend. Dies ware der Fall, wenn 4 eher ein 20n-Elektronensqstem als das postulierte benzoanellierte 16 n-Elektronensqstem aufweisen wiirde. Die Tieffeldverschiebungen der inneren Methylgruppen in 4 sind im Vergleich zu einem zweifach reduzierten System["] jedoch relativ klein. Dies legt nahe, da13 der Grad des Ladungsaustausches zwischen Metall und Ligand klein ist. Wihrend die Stabilitit von Tricarbonylcyclobutadieneisen["] mit der von Fenske['21 vorgeschlagenen Idee der Metalloaromatizitat in Einklang ist. war die Abgabe von formal zwei Elektronen an ein 4n + 2n-Elektronensystem, die ein antiaromatisches Produkt liefert, fur uns iuRerst iiberraschend. Experimen telles Eine Mischung aus [Fe,(CO),] [13] (262 mg. 0.72 mmol) und Benzodihydropyren 2 114) (50 mg. 0.18 mmol) in Benzol (1 mL) wurde unter N, 1 h unter Ruckflu0 geruhrt. Nach dem Abkuhlen wurde der Ruckstand uber Kieselgel chromatographiert (Laufmittel: Petrolether). Die dritte Fraktion enthielt den Komplex 4. Ausheute: 30 mg (40%) dunkelrote Kristalle. Fp = 156°C (Zers., aus Chloroform/Heptan); 'H-NMR (360 MHz. CDCI,, 25°C. StandardCHCI, (6 :=7.240)); 6 =7.24 (m. J(7.8) =7.5 Hz. J(7.9) = 1.5 Hz, J(7.10) = 0.3 Hz. 1 H ; H-7). 6.92 und 6.93 (m, J(8.9) =7.4 Hz, J(8.10) = 1.2 Hz, 2 H . :C: VC'H Vrrlug.sprsrl/schufr mhH. W-6940 Wrinhcrm, /9Y/ 0044-8249/91/0808-/032 $3.50+ .25/6

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The Photochemistry of Nitrogen-Containing Heterocycles

Cited by 14 publications

References 378 publications

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

Cobalt-Mediated [2+2+2] Cycloadditions of Pyrimidine Derivatives to Alkynes

Chemo‐ und stereoselektive Cobalt‐vermittelte [2+2+2]‐Cycloaddition von Alkinen mit Uracil‐Derivaten: Ein neuer Syntheseweg zu modifizierten Nucleosiden

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