Cyclopropenones oxidation

NMR measurements on 2,3-fluorophenylthiirene 1-oxides and 1,1-dioxides show that electron withdrawing conjugative effects are greater for the sulf one than for the sulfoxide and that both are less conjugated than cyclopropenones <79JA390). 

The vertical ionization potentials from the photoelectron spectra of some thiirane and thiirene derivatives are given in Table 3. A Walsh localized scheme of bonding is generally preferred. There is a strong hyperconjugative interaction in thiirene 1,1-dioxides between the occupied C=C tt-MO and the occupied SO2 pure sulfur d-AO. Thiirene oxides are suggested to be less aromatic than cyclopropenones and tropone. 

Oxidative ring expansion occurs when the hydrazine (175) is treated with manganese dioxide (73TL4091). Diphenylcyclopropenone (176) reacts with ammonia and methylamine to give /3-lactams (69BCJ1777). Initial attack could occur at either C-1 or C-2 of the cyclopropenone. 

The [3S+1C] cycloaddition reaction with Fischer carbene complexes is a very unusual reaction pathway. In fact, only one example has been reported. This process involves the insertion of alkyl-derived chromium carbene complexes into the carbon-carbon a-bond of diphenylcyclopropenone to generate cyclobutenone derivatives [41] (Scheme 13). The mechanism of this transformation involves a CO dissociation followed by oxidative addition into the cyclopropenone carbon-carbon a-bond, affording a metalacyclopentenone derivative which undergoes reductive elimination to produce the final cyclobutenone derivatives. 

Since the dipole moments of cyclopropenones are enlarged with respect to simple ketones and compare to other polar systems, e.g. trimethylamine oxide in Table 4, there seems to be evidence for considerable charge separation in the carbonyl group, which was expressed in terms of a cyclopropenium oxide contribution to the ground state. 

Second, cyclopropenone is apparently not completely delocalized and might be regarded as a resonance hybrid 183 of unequivocal contributions a—d which differ in energy and are not simply mixed with equal weight, as implied in the cyclopropenium oxide symbolism hitherto used. 

The 4-hydroxy aryl substituted cyclopropenone 251 was found by West193 to exhibit a remarkable cycle of decarbonylation and oxidation-reduction reactions ... 

The compound 251 decarbonylates on photolysis to bis(4-hydroxyaryl) acetylene 253, which is easily oxidized to the quinonoid cumulene 254. This is also obtained by thermal decarbonylation of the product of oxidation of cyclopropenone 251, the diquinocyclopropanone 252. Likewise, the blue derivative of 3-radialene 256 (a phenylogue of triketo cyclopropane) is formed from tris-(4-hydroxyaryl) cyclopropenium cation 255 by oxidation34. ... 

It should be noted that codimerization was achieved from diphenyl cyclopropenone and unsubstituted cyclopropenone (2JS)197. Phenyl hydroxy cyclopropenone, which appears to be an associated dimer in (dioxane) solution52, formed a dimeric pulviniv acid lactone 260 on treatment with thionyl chloride51, probably via oxidative rearrangement of a dimer 259 ... 

Cyclopropenones can be oxidized according to several methods. When diphenyl cyclopropenone is treated with alkaline H202 desoxybenzoin is formed as the main product and is claimed to arise from primary addition of hydroperoxide ion to the Cl/C2 bond206. Treatment with KMn04 gave benzil67. ... 

Oxidation of diphenyl or di-tert. butyl cyclopropenone with wi-chloro peroxy-benzoic acid207 proceeds via intermediates corresponding to a Bayer-Villiger-type mechanism 277/278) to unrearranged products (1,2-diketones) or rearranged products (ketones) depending on the reaction conditions. 

Diphenylcyclopropene thione is transformed to diphenyl cyclopropenone by means of lead tetraacetate (presumably via 279/280), whilst perphthalic acid oxidizes to cation 281, which gives the unstable S-oxide 282 with NaHC03208. ... 

Arylidene alkylamines and diphenyl cyclopropenone gave rise to products 397-399, whose formation can be interpreted by means of oxidative secondary reactions of the 5 H-A2-pyrrolin-4-one 396 (R2 = H) initially generated252. ... 

Analogously, the mesoionic jV-methyl thiazol-5-ones and l,3-dithiol-4-ones afforded A-methyl-4-pyridones and thiapyran-4-ones when reacting with diphenyl cyclopropenone and its thione261. Benzonitrile oxide apparently gives a 1,3-dipolar cycloaddition to the C=0 group of diphenyl cyclopropenone rationalizing the formation of triphenyl-l,3-oxazin-6-one 41626i ... 

Tetracyano ethylene oxide, however, which represents a potential 1,3-dipole of the carbonyl ylide type, reacts with diphenyl cyclopropenone to give a cycloadduct of probable structure 415/417263, which may arise from insertion into the cyclopropenone C1(2)/C3 bond. 

An analogy with reductive dimerization of diphenyl cyclopropenone (p. 58) was found on polarography of l,2-diphenyl-4,4-dicyano triafulvene (64)289. In a one-electron reduction step the cyclopropenyl radical anion 469 is likely to be generated and dimerized to the dianion of tetraphenyl-l,4-dicyanomethyl benzene (470) the dianion 471 could be successively oxidized via the anion radical 472 to the 1,4-quinodimethane derivative 473. 

It is interesting to note that according to Ref.136) regardless of the model used, the CNDO/2 treatment predicts a larger ir-polarization for cyclopropenone than for tropone. This means that the electrostatic work to achieve a cyclopropenium oxide structure is considerably less than for cycloheptatrienylium oxide. From this reason, cyclopropenone seems to be a closer approximation to an aromatic system than tropone which can be described better as a polyolefin. 

Radialenes which are structurally related to 44, i.e. cyclopropanes bearing two quinoid and another acceptor-substituted methylene substituent, were obtained by condensation of bis(4-hydroxyphenyl)cyclopropenones with active methylene compounds, followed by oxidation (Scheme 6)19. Radialenes 45a-f are brilliantly colored solids that are blue or blue-violet in solution but appear metallic gold or red in reflected light. Instead... 

When pyridinium A -imine salts 157 were reacted with methylphenyl-cyclopropenone (158, R = Ph, R = Me) in the presence of a base, dihydro-pyrido[l,2-h]pyridazin-3-ones (159) were formed, which subsequently underwent oxidation to produce 3//-pyrido[l,2-h]pyridazin-3-ones (160) under the reaction conditions [76JCS(CC)275 78JOC2892], In some cases the dihydro intermediates (159) could be isolated. 3-Substituted derivatives (157, R = 3-Me, 3-CN R = H) gave mixtures of isomers of 160 (R = 5-... 

Bernhardsson and coworkers have recently used CASPT2 calculations (electron-correlation correction to the CAS wave function) to model carbonyl oxides in solution. Solvation effects in acetonitrile solvent also suggest that the zwitterionic form would be favored with an elongation of the 0—0 bond length and a decrease in the C—O bond. Ab initio calculations have been recently reported for monofluorocarbonyl oxide , diflu-orocarbonyl oxide , methylcarbonyl oxide and cyclopropenone carbonyl oxide. In the recent literature the idea that carbonyl oxide can be an important source of OH radicals has also been presented. ... 

Alternatively, cyclopropenones give rise to [2 + 3] bicycloadducts with nitrile oxides, or ylides, which readily rearrange to yield l,3-oxazin-6-ones. If cyclopropenethiones are employed l,3-oxazin-6-thiones are formed (Scheme 78) (72CJC584). 

CYCLOADDITION N-Alkylhydroxy-lamines. f-Butyldimethylsilyl ethylnitron-ate. Cyclopropenone 1,3-propanediyl ke-tal. Hydrogen peroxide-Sodium tungstate. N-Methylhydroxylamine. Phenyl isocyanate. Trimethylamine N-oxide. Trimethylsi-lylmethyl azide. 

Cyclopropenon Bis-[dimethylamino]-E17d, 2992/3136 (NR2 Oxo) Diazen 1-(1-Cyclohexenyl)-2-methyl- -1-oxid E15/1, 1092 (N-Oxigenier.)... 

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