π-Facial stereoselectivity in the Diels–Alder reactions of benzene oxides

Gillard, James; Newlands, M. J.; Bridson, John N.; Burnell, D. Jean

doi:10.1139/v91-199

Cited by 51 publications

(53 citation statements)

References 16 publications

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“…This gave a single adduct 294b,295b, whose structure was validated by NMR and X-ray diffraction, showing that the dienophile approaches the diene anti to the epoxide moiety of the diene. These data are consistent with the previous adducts of benzene oxide obtained with other dienophiles [307,308] and with other studies carried out recently by Harper and co-workers [35c]. The reaction of 293a/b with 291a gave two adducts, one of which is the expected [1 þ 1] adduct 296b (derived from 293b) and shows again the preference for anti addition (dienophile versus epoxide) and the second adduct arises from two molecules of dienophile 291a and one molecule of 293a/b (Scheme 21.138).…”

Section: Cycloaddition Reactionssupporting

confidence: 93%

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Vaquero

Cuadro

Herradón

2011

Modern Heterocyclic Chemistry

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The replacement of a carbon atom by a heteroatom in a seven-membered carbocycle leads to the corresponding seven-membered heterocyclic ring system. Different types of heterocycles can be formed depending on the nature of the carbocycle. In a cycloheptatriene the replacement can involve any of the six sp 2 hybridized carbons or the sp 3 carbon atom, whereas in cycloheptane all carbon atoms are equivalent and replacement affords exclusively the fully saturated heterocyclic systems. Partially saturated seven-membered heterocycles can be viewed as derivatives or related systems of these two main seven-membered heterocyclic units arising from carbon replacement in cycloheptatriene and in cycloheptane. Replacement of the sp 3 hybridized carbon atom in cycloheptatriene by a nitrogen leads to an azacycloheptatriene known as 1H-azepine (1) and the corresponding 2H-, 3H-, and 4H-azepines (2-4) are the tautomeric forms generated by the replacement of the sp 2 carbons. 1H-Azepine is an unstable red oil that is prone to rearrange to the also unstable 3H-azepine in the presence of acids and bases. However, this tautomer seems to be more stable than both 4H-and 2H-azepine. The structures related to 1H-azepine that bear an oxygen or sulfur atom are known as oxepine (5) and thiepine (6) (thiepin is favored by Chemical Abstracts Service). Oxepine is much more stable than thiepine and has been synthesized, isolated, and characterized at room temperature while thiepine has not been detected to date. Stable monocyclic thiepines were prepared and characterized in the 1980s. Azepines, oxepines, and thiepines that are constrained to planar or almost planar conformations should be antiaromatic molecules with negative resonance energy and, as a consequence, these compounds are unknown.The fully saturated seven-membered heterocycle containing one nitrogen is azepane (7) (hexahydroazepine or perhydroazepine); the oxygen and sulfur analogues are known as oxepane (8) and thiepane (9). All of these compounds are stable and show typical behavior of secondary amine, ether and thioether, respectively. TwoModern Heterocyclic Chemistry, First Edition. Edited

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Section: Cycloaddition Reactionssupporting

confidence: 93%

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Vaquero

Cuadro

Herradón

2011

Modern Heterocyclic Chemistry

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“…In short, dibromination of 1,4-cyclohexadien with elemental Br 2 in chloroform at 0°C led to 4,5-dibromocyclohexene (van Tamelen 1955). The oxidation of 4,5-dibromocyclohexene leading to 4,5-dibromocyclohexene oxide was realized with m -chloroperoxybenzoic acid ( m CPBA) (Gillard et al 1991). Benzene oxide was formed by further dehydrobromination with diazobicyclo [5.4.0] undec-7-ene (DBU) mixed with acetonitrile (1:4).…”

Section: Methodsmentioning

confidence: 99%

Benzene oxygenation and oxidation by the peroxygenase of Agrocybe aegerita

et al. 2013

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Aromatic peroxygenase (APO) is an extracellular enzyme produced by the agaric basidiomycete Agrocybe aegerita that catalyzes diverse peroxide-dependent oxyfunctionalization reactions. Here we describe the oxygenation of the unactivated aromatic ring of benzene with hydrogen peroxide as co-substrate. The optimum pH of the reaction was around 7 and it proceeded via an initial epoxide intermediate that re-aromatized in aqueous solution to form phenol. Identity of the epoxide intermediate as benzene oxide was proved by a freshly prepared authentic standard using GC-MS and LC-MS analyses. Second and third [per]oxygenation was also observed and resulted in the formation of further hydroxylation and following [per]oxidation products: hydroquinone and p-benzoquinone, catechol and o-benzoquinone as well as 1,2,4-trihydroxybenzene and hydroxy-p-benzoquinone, respectively. Using H218O2 as co-substrate and ascorbic acid as radical scavenger, inhibiting the formation of peroxidation products (e.g., p-benzoquinone), the origin of the oxygen atom incorporated into benzene or phenol was proved to be the peroxide. Apparent enzyme kinetic constants (kcat, Km) for the peroxygenation of benzene were estimated to be around 8 s-1 and 3.6 mM. These results raise the possibility that peroxygenases may be useful for enzymatic syntheses of hydroxylated benzene derivatives under mild conditions.

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“…Mass spectrum of second product (retention time = 4.0 min) corresponds to that published for benzene oxide (BO). [8,18] Mass spectra of this product derived from C 6 ) differed on m/z 6 indicating the presence of all six H/D atoms on benzene core. The authentic benzene oxide was prepared according to published protocols.…”

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confidence: 95%

N‐Bridged Diiron Phthalocyanine Catalyzes Oxidation of Benzene with H₂O₂ via Benzene Oxide with NIH Shift Evidenced by Using 1,3,5‐[D₃]Benzene as a Probe

Kudrik¹,

Sorokin²

2008

Chemistry A European J

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The ability of cytochromes P-450 and methane monooxygenases (MMO) to catalyse difficult oxidations of hydrocarbons have inspired numerous biomimetic studies. The progress in this challenging field deals with the development of metalloporphyrin-based systems [1] as well as mononuclear [2] and binuclear [3] iron non-heme complexes. Cytochrome P-450 chemistry involves mononuclear porphyrin complexes, while MMO chemistry is based on binuclear iron non-heme complexes. It should be noted that mimicking of the structural organisation and spectroscopic features of MMO has been achieved using diiron non-heme complexes, but no functional models able to oxidize methane have been published.[3a] One interesting possibility is to explore binuclear macrocyclic porphyrin-like complexes as oxidation catalysts. However, this approach has not yet been developed.Our ongoing research is focused on developing clean oxidation processes using phthalocyanine complexes, [4, 5] which are structurally relevant to porphyrins, but cheap and readily accessible on a large scale. Inspired by the observation that iron phthalocyanine supported in m-oxo dimeric form (Fe-O-Fe motif) showed superior catalytic properties in the selective oxidation than monomeric FePc, [6] we have investigated catalytic properties of diiron phthalocyanines. NBridged binuclear complexes (metal-N-metal motif) constitute another family of dimers. Several m-nitrido dimeric complexes with different ligands have previously been described. [7] To the best of our knowledge, these unusual complexes with interesting properties have never been used as oxidation catalysts. In particular, the unsubstituted (FePc) 2 N dimer, insoluble in organic solvents, contains Fe III -N=Fe IV fragment with one unpaired electron delocalized between two equivalent Fe sites with formal + 3.5 state as was deduced from Mçssbauer data (d = 0.06 mm s À1

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π-Facial stereoselectivity in the Diels–Alder reactions of benzene oxides

Cited by 51 publications

References 16 publications

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Benzene oxygenation and oxidation by the peroxygenase of Agrocybe aegerita

N‐Bridged Diiron Phthalocyanine Catalyzes Oxidation of Benzene with H₂O₂ via Benzene Oxide with NIH Shift Evidenced by Using 1,3,5‐[D₃]Benzene as a Probe

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π-Facial stereoselectivity in the Diels–Alder reactions of benzene oxides

Cited by 51 publications

References 16 publications

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Seven‐Membered Heterocycles: Azepines, Benzo Derivatives and Related Systems

Benzene oxygenation and oxidation by the peroxygenase of Agrocybe aegerita

N‐Bridged Diiron Phthalocyanine Catalyzes Oxidation of Benzene with H2O2 via Benzene Oxide with NIH Shift Evidenced by Using 1,3,5‐[D3]Benzene as a Probe

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N‐Bridged Diiron Phthalocyanine Catalyzes Oxidation of Benzene with H₂O₂ via Benzene Oxide with NIH Shift Evidenced by Using 1,3,5‐[D₃]Benzene as a Probe