Substituent effects in arosemibullvalene photochemistry: the methylcyclopropane rearrangement of 1,8-dimethylbenzosemibullvalene

Bender, Christopher Owen; Bengtson, D. L.; Dolman, Douglas; Herle, Carolyn Elaine L.; O'Shea, Seamus F.

doi:10.1139/v82-272

Cited by 15 publications

(7 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For general background to photochemical conversions of benzocyclooctatetraenes, see: Bender et al (1982Bender et al ( , 1986Bender et al ( , 1988Bender et al ( , 1991. For details of the synthesis, see: Barton et al (1964).…”

Section: Related Literaturementioning

confidence: 99%

(5Z,7Z,9Z)-5,10-Dibromobenzo[8]annulene

Bender¹,

Boeré²

2013

Acta Cryst E

View full text Add to dashboard Cite

In the structure of the title compound, C12H8Br2, the two bromine substituents are oriented exo to the boat-shaped cyclooctatetraene at the two ring sites that are β to the ring fusion positions. The average Br—C bond distance is 1.919 (2) Å, the average distance for C=C double bonds that are Br substituted is 1.328 (2) Å, while the other two double-bond distances are 1.327 (2) and 1.398 (2) Å for the non-fused and fused bonds, respectively. Each type of ring interatomic distance is within s.u. of the average values for the four known structures, including the title compound, of benzo-fused cycloocatatetraenes that are not coordinated to a metal atom. The crystal structure features short Br⋯Br [3.6620 (3) Å] and C⋯H [2.834 (2) and 2.841 (2) Å] contacts.

show abstract

Section: Related Literaturementioning

confidence: 99%

(5Z,7Z,9Z)-5,10-Dibromobenzo[8]annulene

Bender¹,

Boeré²

2013

Acta Cryst E

View full text Add to dashboard Cite

show abstract

“…The quantum yield for the conversion of COT 1+2 was performed on an apparatus previously described (9), which includes an optical bench arranged for beam splitting into a potassium ferrioxalate actinometer (10). Cyclohexane solutions (in Cell C, 3.5 mL) of COT 2 (8 x M) were deoxygenated prior to irradiation by flushing with argon.…”

Section: Quanturn Efficienciesmentioning

confidence: 99%

Mechanistic variations in the formation of benzocyclooctatetraene from benzobicyclo[4.2.0]octa-2,4,7-triene

Bender¹

1996

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

Benzocyclooctatetraene (i.e., COT, 2) is the major product from the thermolysis and direct photolysis of 2,3-benzobicyclo[4.2.0]octa-2,4,7-triene (i.e., triene 1). It is also a minor product from the sensitized irradiation of 1. The mechanism of the reaction 1 → 2 was investigated using deuterium-labelled triene (i.e., 1a/b), which was prepared in a two-step procedure from a known triene mixture (1a) containing deuterium at both C-4 (43%) and C-5 (97%): the thermolysis of 1a led to labelled COT 2a, which upon direct irradiation (λ ≥ 310 nm) gave the deuterated triene mixture 1a/b in good chemical yield (61%) but in low quantum efficiency (Φ ≈ 0.0001). The COT produced from the direct irradiation (Corex filter) of 1a/b possessed different deuterium distributions than when generated thermally or from triplet sensitization (p-dimethylaminobenzophenone), as determined by 1H NMR integration. The observed deuterium-labelling patterns are in accord with a Zimmerman di-π-methane rearrangement being involved in formation of the COT from S1, of triene 1, while a mechanism proceeding by initial cleavage of the cyclobutene C1—C6 bond appears to operate during the thermal or sensitized (T1) generations of 2. Key words: mechanisms, rearrangements, photochemistry, di-π-methane.

show abstract

“…Quantum yields were performed on an apparatus previously described (20), which includes an optical bench arranged for beam splitting into a femoxalate actinometer (21). Cyclohexane solutions (3.5 mL) of reactants (ca.…”

Section: Quatztum Yield Determinationsmentioning

confidence: 99%

The photochemistry of 1-cyano-2,3-benzobicyclo[4.2.0]octa-2,4,7-triene

Bender¹,

Clyne²,

Dolman³

1991

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

The title compound (10) wasprepared, along with the4-cyano isomer (11), by the direct irradiation of 5-cyanobenzocyclooctatetraene (9); the yields were 82% (Dlo = 0.0030) and 12% (@,, = 0.0004) respectively. Triene 10 was thermally and photochemically reactive. Heating solutions of 10 at 150°C for 1 h gave COT 9 quantitatively. On direct irradiation 10 forms 5-cyanobenzosernibullvalene (12; 5%, @ = 0.019), COT 9 (70%, @ = 0.56), and 1-cyanonaphthalene (14%, @ = 0.078). Sensitized irradiation of 10 gave 9 exclusively (92%, @ = 0.88). COT 9 was also produced by the direct irradiation of semibullvalene 12 (75%, @ = 0.13). Studies with deuterium labelled 10 suggest that the photoformation of COT 9 involves a simple electrocyclic opening of the cyclobutene ring of the triene. Additionally, the labelling results indicate that the formation of semibullvalene 12 from 10 derives from the operation of two reaction pathways, the major one of which appears to be a Zimmerman di-T-methane rearrangement. The mechanism proposed for the minor pathway to 12 has not been observed in other bicyclo A 150"C, des solutions de 10 se transforment en 9 en rendements quantitatifs. Par irradiation directe, 10 conduit au cyano-5 benzo semi-bullvaltne (12; 5%, @ = 0.019), a 9 (70%, @ = 0.56) et au cyano-1 naphtalkne (l4%, @ = 0.078). Par irradiation sensibiliste, 10 conduit a 9 uniquement (92%, @ = 0.88). Le compose 9 se forme aussi de la photolyse directe du semi-bullvaltne 12 (75%, @ = 0.13). Des ttudes de marquages au deuterium suggkrent que 9 se produit photochirniquement du tritne par un mtcanisme qui comporte l'ouverture electrocyclique de l'anneau du cyclobuttne de 10. De plus, des etudes de marquages dtmontrent qu'il y a deux mecanismes qui entrent en jeux dans la transformation 10-12. Le mkcanisme majeur derive d'une transposition di-T-mithane de Zimmerman. Un nouveau mtcanisme est propos6 pour la voie mineure qui fournit 12.

show abstract

Substituent effects in arosemibullvalene photochemistry: the methylcyclopropane rearrangement of 1,8-dimethylbenzosemibullvalene

Abstract: . Can. J. Chem. 60, 1942Chem. 60, (1982.

Cited by 15 publications

References 9 publications

(5Z,7Z,9Z)-5,10-Dibromobenzo[8]annulene

(5Z,7Z,9Z)-5,10-Dibromobenzo[8]annulene

Mechanistic variations in the formation of benzocyclooctatetraene from benzobicyclo[4.2.0]octa-2,4,7-triene

The photochemistry of 1-cyano-2,3-benzobicyclo[4.2.0]octa-2,4,7-triene

Contact Info

Product

Resources

About