The Azo(Azoxy) Functionality as a π2 Component in Photo [2+2] cycloadditions ‘syn’‐ and ‘anti’‐3,4‐diazatricyclo[4.2.2.22,5]dodeca‐3,7‐diene, syntheses, photolyses, X‐ray‐structure analysis, and PE spectra

Marterer, Wolfgang; Prinzbach, Horst; Rihs, Grety; Wirz, Jakob; Lecoultre, Jacques; Heilbronner, E.

doi:10.1002/hlca.19880710813

Cited by 23 publications

References 111 publications

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Proximate,syn-Periplanar, Rigid Imine(Nitrone)/Ene-, and Diazene(Diazeneoxy)/Ene Systems: Syntheses, Homoconjugate Reactivity and Photochemistry

Fischer¹,

Fritz

Rihs

et al. 2000

Eur. J. Org. Chem.

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The chances for intramolecular imine/ene (→ azetidines), diazene/ene (→ 1,2‐diazetidines), diazeneoxy/ene (→ 1,2‐diazetidine oxides) and diazenedioxiene (→ 1,2‐diazetidine dioxides) [2+2]photocycloadditions and for the isolation of the respective photoproducts, have been probed with specifically designed substrates. Upon direct or sensitized excitation, [2+2]cycloaddition was found to be the exclusive or at least dominant chemical process for the CN/CC, NN/CC and ONN(O)/CC systems featuring very small π,π‐distances of 2.8‐3.0 Å and large π,π‐interorbital angles of 160‐170° (7 → 51, 17 → 55, 33 → 58 (competing N2 elimination), 22 → 62). This is not the case, however, in ONNO/CC (23, where electron transfer is a possibility), or in the more flexible, less “proximate” CN/CN (57) and CNO/CN (63) systems (π,π‐distances of >3.8 Å). While the corseted 1,2‐diazetidine photoadducts (55, 58) proved to be thermally stable, their N‐oxides (62, 65) were thermally too labile to be directly observable above ‐65 °C. For the latter's only fleeting existence, electronic rather than strain effects are held responsible (B3LYP/6‐31G* calculations). Very facile CNO/CC (12 → 13) and NNO/CC (22 → 24) [3+2]cycloadditions, homoconjugate addition of H2 and of dienophiles ([2+2+2]) to the diazene/ene 17 (→ 39, 41, 45) are manifestations of “proximity” in these bichromophoric skeletons.

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Proximate,syn-Periplanar, Rigid Imine(Nitrone)/Ene-, and Diazene(Diazeneoxy)/Ene Systems: Syntheses, Homoconjugate Reactivity and Photochemistry

Fischer¹,

Fritz

Rihs

et al. 2000

Eur. J. Org. Chem.

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Proximate,syn-Periplanar Bisdiazene Skeletons: Syntheses, Structures, Homoconjugate Reactivity and Photochemistry

Exner¹,

Fischer

Bahr

et al. 2000

Eur. J. Org. Chem.

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Rigid NN/NN (diazene/diazene) systems (F) consisting of more or less alkylated DBH and DBO chromophoric units (1, 2, X‐ray structures), with very short π,π distances [d = 2.849 (1a, av.), 2.822 Å (2)] and almost perfect syn‐periplanar π,π alignments [ω = 168.6 (1a), 174.2° (2)] as well as the more flexible, less “proximate” metathesis isomers (3a,c, 27a,c, d >4.6 Å, ω = 90‐100°) have been synthesized. Homoconjugate π,π interaction (in 1, 2, not in 3, 27) is deduced from UV spectroscopic measurements [π → π* maxima at 239 (234) nm (sh, 260)], while PE analyses furnished only small interaction parameters (1a: <0.3 eV). The potential of the novel syn‐periplanar NN/NN motif in 1 and 2 for the synthesis of somewhat exotic polyheterocycles has been explored by calculation (B3LYP) as well as experimentally: i.a. kinetically stabilized, all‐cis‐peralkylated tetrazolidines (38, 44) and perhydro‐1,2,4,5‐tetrazines (41, 47) have become accessible (i.a. via novel azomethine/diazene and azomethine/azomethine cycloadditions). In 1a with its unreactive DBO chromophoric subunits, in the “buttressed” derivatives 1b‐d, as well as in the DBH/DBO combination 2, and likewise in more ‘distant’ 27 (differently from the analogous CC/CC and NN/CC systems), irrespective of the excitation conditions employed (light of λ ≥≥ 280, 254 nm, low temperature matrix irradiation, acetone sensitization) no [2+2]photocycloaddition was observed. Instead exclusively N2‐elimination took place. It is argued that unproductive NN/NN photocycloaddition would have become observable through metathesis isomerization of the respective tetrazetidines.

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Zur Existenz nichtklassischer, cyclisch delokalisierter 4N/5e-Radikalanionen und 4N/6e-Dianionen – Ein- und Zweielektronen-Reduktion nahgeordneter, synperiplanarer Bisdiazene

et al. 1998

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The Azo(Azoxy) Functionality as a π₂ Component in Photo [2+2] cycloadditions ‘syn’‐ and ‘anti’‐3,4‐diazatricyclo[4.2.2.2^2,5]dodeca‐3,7‐diene, syntheses, photolyses, X‐ray‐structure analysis, and PE spectra

Cited by 23 publications

References 111 publications

Proximate,syn-Periplanar, Rigid Imine(Nitrone)/Ene-, and Diazene(Diazeneoxy)/Ene Systems: Syntheses, Homoconjugate Reactivity and Photochemistry

Proximate,syn-Periplanar, Rigid Imine(Nitrone)/Ene-, and Diazene(Diazeneoxy)/Ene Systems: Syntheses, Homoconjugate Reactivity and Photochemistry

Proximate,syn-Periplanar Bisdiazene Skeletons: Syntheses, Structures, Homoconjugate Reactivity and Photochemistry

Zur Existenz nichtklassischer, cyclisch delokalisierter 4N/5e-Radikalanionen und 4N/6e-Dianionen – Ein- und Zweielektronen-Reduktion nahgeordneter, synperiplanarer Bisdiazene

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