16204-36-7Relevant academic research and scientific papers
Ozonation of 1,1,2,2-tetraphenylethene revisited: Evidence for electron- transfer oxygenations
Schank, Kurt,Beck, Horst,Buschlinger, Michael,Eder, Joerg,Heisel, Thomas,Pistorius, Susanne,Wagner, Christiane
, p. 801 - 826 (2007/10/03)
Ozonolyses of 1,1,2,2-tetraphenylethene (TPE, 1) have been described many times in the literature, but the reports are contradictory. This reaction is particularly important for understanding the mechanism of alkene ozonolysis, in view of possible stabilization of reactive intermediates by aryl groups. Thus, systematic investigations of ozonolysis in both aprotic solvents and in protic solvents are reported here. Attention is directed to the following details that have been underestimated in the past: i) the actual electronic structure of ground-state ozone (O3), ii) differentiation between strained and unstrained alkenes, iii) the significance of both the O3 concentration and the TPE concentration, iv) the influence of various solvents, including pyridine, v) the influence of the reaction temperature, vi) the role of electron-transfer catalysis (ETC) and, yii) the effect of structural modifications. Our results suggest that ozonolysis of TPE (1) does not include a 1,3-dipolar reaction step, but represents a particularly interesting example of electron-donor (TPE)/electron-acceptor (O3) redox chemistry. The present investigations include several crucial results. First, pure 3,3,6,6-tetraphenyltetroxane (3, m.p. 221°(dec.)) and pure tetraphenylethylene ozonide (4, m.p. 153°(dec.)) are prepared for the first time, although 3 and 4 have long been known. Second, the singlet diradical character of O3, lessened by means of hypervalent-electron interaction and predicted by different calculations, is evidenced via reaction with the spintrap galvinoxyl (2,6-bis(1-1-dimethylethyl)-4-{[3,5-bis(1,1- dimethylethyl)-4-oxocyclohexa-2,5-dien-1-ylidene]methyl}phenoxy; 8), and the zwitterionic reaction behavior of ground-state O3 is ruled out. Third, the electronacceptor ability of O3 is evidenced by reactions with suitable tetraaryl ethylenes: it is enhanced by addition of catalytic amounts of protons or Lewis acids. Fourth, the observed distribution of the O3 O-atoms to the two different olefinic C-atoms of the unsymmetric alkene 27b is in full agreement with an initial single-electron transfer (SET) step, followed by a radical mono-oxygenation to cause the crucial C,C cleavage. Final dioxygenation should lead to the generally known products (ozonides, tetroxanes, hydroperoxides). The regioselectivity is found to be inconsistent with the expected decay of an intermediate primary ozonide. Finally, the treatment of 1,2-bis(4-methoxyphenyl)acenaphthylene (36) with O3 (simultaneous transfer of three O-atoms) leads to the same experimental result as a stepwise transfer of one O-atom followed by a transfer of two O- atoms.
Synthesis of 3-Vinyl-1,2,4-trioxolanes by a Cycloaddition of Carbonyl Oxides with α,β-Unsaturated Carbonyl Compounds
Mori, Mitsuyuki,Tabuchi, Toshihiko,Nojima, Masatomo,Kusabayashi, Shigekazu
, p. 1649 - 1652 (2007/10/02)
The cycloaddition of a carbonyl oxide, generated by the ozonolysis of a vinyl ether, to an α,β-unsaturated aldehyde gave the 3-vinyl-1,2,4-trioxolane (α-vinyl ozonide) in moderate yield.In contrast, α,β-unsaturated ketones showed a very poor reactivity with carbonyl oxides.Benzylidenecyclohexanones were exceptions, from which the corresponding 3-vinyl-1,2,4-trioxolanes were obtained in excellent yields.Reaction of the 3-vinyl-1,2,4-trioxolanes with ozone led to the formation of the corresponding diozonides.
Ozonolysis of Vinyl Ethers in the Presence of α-Diketones and α-Keto Esters
Tabuchi, Toshihiko,Nojima, Masatomo
, p. 6591 - 6595 (2007/10/02)
Ozonolysis of vinyl ethers in the presence of α-diketones provided two types of products, i.e., a Baeyer-Villiger oxidation product and 3-acyl-1,2,4-trioxolane.The evidence suggests that the latter product is labile and, therefore, the former one might be produced by decomposition of the latter.In contrast, 1,2,4-trioxolane-3-carboxylates were stable.As a result, ozonolysis of vinyl ethers in the presence of α-keto esters yielded the expected ozonides in high yield.
Ozonolysis of Vinyl Ethers in Solution and on Polyethylene
Griesbaum, Karl,Kim, Woo-Sun,Nakamura, Norinaga,Mori, Mitsuyuki,Nojima, Masatomo,Shigekazu, Kusabayashi
, p. 6153 - 6161 (2007/10/02)
Ozonolyses of the vinyl ethers 1a-f in methanol afforded almost exclusively the corresponding α-methoxy hydroperoxides 4, suggesting the preferred formation of the carbonyl oxides 2.In aprotic solvents including methyl formate, the predominant modes of decay of the carbonyl oxides 2 were cyclodimerization, reduction, and rearrangement, yet no ozonide formation.By contrast, ozonolyses of 1a-f on polyethylene gave the α-methoxy-substituted ozonides 14 in fair yields.Ozonolyzes of 1a-f in the presence of added carbonyl compounds 6 in methylene chloride or ether yielded the corresponding cross ozonides.Judged from the ozonide yields, the reactivities of the carbonyl compounds follow the sequence: (ClCH2)2C=O > ClCH2COCH3 > (CH3)2C=O and 2-CF3C6H4CHO > PhCHO.
