485-46-1Relevant academic research and scientific papers
6,7-Benzotropolone Syntheses Based on Ring-Closing Metatheses and Four-Electron Oxidations
Brückner, Reinhard,Fernandes, Manuel A.,Gemander, Manuel,Green, Ivan R.,Kreibich, Michael,Peter, David,Yadav, Dharmendra B.,de Koning, Charles B.,van Otterlo, Willem A. L.
, (2020/05/18)
Four homoallyl ortho-vinylaryl ketones (10a-d) – 1,8-dienes of sorts – were prepared by several approaches. In the presence of 1–2 mol-% Grubbs-II catalyst, they ring-closed to give 6,7-dihydrobenzocyclohepten-5-ones (11a-d) in 90–96 % yield. With SeO2 the parent compound (11a) delivered benzocyclohepten-5-one (13a) and/or selenium-containing compounds (18–22) but no more than traces of 6,7-benzotropolone (5a). However, 5a was accessible from compound 11a via the sodium enolate and allowing it to react with a stream of oxygen (43 % yield). The sodium enolates of the substituted 6,7-dihydrobenzocyclohepten-5-ones 11b–d and oxygen underwent analogous 4-electron oxidations. This furnished the substituted 6,7-benzotropolones 11b-d. In contrast, the corresponding lithium enolates were inert towards oxygen. The 6,7-dihydrobenzocyclohepten-5-one 11d was also accessed differently, namely by a Grubbs-II catalyst-mediated RCM/C=C migration tandem reaction of the allyl ortho-allylaryl ketone 73 – another 1,8-diene of sorts (90 % yield).
Access to the naphthylcarbene rearrangement manifold via isomeric benzodiazocycloheptatrienes
Bonvallet, Paul A.,Todd, Eric M.,Kim, Yong Seol,McMahon, Robert J.
, p. 9031 - 9042 (2007/10/03)
Irradiation (λ = 670 or >613 nm) of 4,5-benzodiazocycloheptatriene (15), matrix isolated in argon at 10 K, produces primarily 2,3-benzobicyclo[4.1.0]hepta-2,4,6-triene (9) accompanied by small amounts of triplet 4,5-benzocycloheptatrienylidene (2) and 2-naphthylcarbene (10). A reversible photoequilibrium is established in which 9 is converted to 10 at λ = 290 nm and then regenerated at λ = 360 nm. Similarly, matrix-isolated 2,3-benzodiazocycloheptatriene (16) produces 4,5-benzobicyclo[4.1.0]hepta-2,4,6-triene (11) at λ = 670 or >613 nm, but without detection of 2,3-benzocycloheptatrienylidene (4). Irradiation of 11 at λ = 290 nm induces ring opening to triplet 1-naphthylcarbene (12), which, in turn, cyclizes back to 11 at λ = 342 or >497 nm. The diazo compounds and photoproducts are characterized by IR, UV/visible, and ESR spectroscopy, where appropriate, and by comparison of the experimental and B3LYP/6-31G* calculated IR spectra for each species. Alternate rearrangement products such as allenes 6, 7, and 8 are not detected in the photolysis of either diazo compound.
Iodine(V) reagents in organic synthesis. Part 4. o-Iodoxybenzoic acid as a chemospecific tool for single electron transfer-based oxidation processes
Nicolaou,Montagnon,Baran,Zhong
, p. 2245 - 2258 (2007/10/03)
o-Iodoxybenzoic acid (IBX), a readily available hypervalent iodine(V) reagent, was found to be highly effective in carrying out oxidations adjacent to carbonyl functionalities (to form α, β-unsaturated carbonyl compounds) and at benzylic and related carbon centers (to form conjugated aromatic carbonyl systems). Mechanistic investigations led to the conclusion that these new reactions are initiated by single electron transfer (SET) from the substrate to IBX to form a radical cation which reacts further to give the final products. Fine-tuning of the reaction conditions allowed remarkably selective transformations within multifunctional substrates, elevating the status of this reagent to that of a highly useful and chemoselective oxidant.
THE OXIDATION OF BENZOTROPYLIUM CATION
Pomerantz, Martin,Swei, Gwo-Shin
, p. 3027 - 3030 (2007/10/02)
Oxidation of benzotropylium (1) fluoborate with Na2O2 and KO2 gives the benzotropones, 5 and 6, as the major products with no naphtalene (9) or other ring contracted products formed.Oxidation with m-chloroperoxybenzoic acid produces a small amount of naphtaldehydes (10 and 11) and even less naphtalene, along with the benzotropones, while oxidation with H2O2 and t-butyl peroxyacetate gives slightly more of the ring contracted naphtaldehydes than benzotropones, in addition to a small quantity of naphtalene.All reactions produce some 1,2-benzotropolidine (8).
