Cyclo Propenone

Another convenient approach to the azapentatriafulvalene system is given by the in situ formation of cyclopropenylium salts from cyclo-propenones and dry HCl gas followed by their electrophilic attack on various indoles. Tire corresponding heterofulvalenium salts of type 35 were isolated as chlorides, which were somewhat photosensitive and thermally labile (68TL5537). 

In this article it is intended to give a collective and comparative survey of cyclo-propenone and triafulvene chemistry in the following areas ... 

This method has also been used for the preparation of a series of aryl phenyl cyclo-propenones,6 ... 

Attempts were reported119,129 to synthesize the ortho-linked diphenyl cyclo-propenone phenanthreno cyclopropenone 173 by dehydrohalogenation of the dibromo derivative 174 of dibenzo cyclohepta-l,3-diene-6-one. The only product isolated was the anhydride 175 of phenanthrene-9-carboxilic acid, which was shown not to arise from 173l29 ... 

Robin et al.162 investigated the photoelectron spectrum of unsubstituted cyclo-propenone and interpreted its results with the aid of Gaussian-type orbital calculations of double-zeta quality for the electronic ground state using the experimentally established133 geometry of cyclopropenone. 

Reactions with cyclopropene.11 Lithium organocuprates react with the cyclo-propenone ketal 1 (12, 152-154) to form a copper species (a) that behaves as an enolate of a cyclopropanone. Thus it reacts with alkyl halides to form cis-2,3-disubstituted derivatives of 1. 

PREPARATION AND THREE-CARBON + TWO-CARBON CYCLOADDITION OF A CYCLOPROPENONE KETAL CYCLO-PROPENONE 1,3-PROPANEDIOL KETAL... 

The by now well-established flash vacuum pyrolysis methods (FVP) can also be applied in the field of ynamine synthesis. Thus norbomenyl ynamine 92 fragments at 500° to vinyl ynamine 93 in almost quantitative yield (145) 165). FVP of diamino cyclo-propenones gives ynediamines in very good yields (146) 166 . 

Cyclopropenes and cyclopropenones can also be used as precursors for expanded ring systems. The intermediates of the ring enlargement reactions are generated by 1,3-dipolar addition or by a [2+2] addition across the cyclo-propenyl jr-bond [55]. The reaction principle is summarized in Scheme III/7. In the addition of a 1,3-dipole (III/42) to a cyclopropene, III/41, the bicyclic compound III/43 is formed. Depending on several factors the primary reaction product, III/43, may be stable. In cases where III/43 is formed from cyclo-propenone, it may eliminate carbon monoxide to yield the five-membered III/44. An alternative reaction possibility for III/43 is its spontaneous rearrangement to the monocyclic compound, III/45. Acylic decomposition products of compound III/43 are known, too. 

Both H and C NMR spectra have been recorded for 8 at 193 K in acetone-d and at 213 K in a trichlorofluoromethane/l,2-dibromotetrafluoroethane/acetone-d6 (5 5 1) mix-ture. The fact that the compound has been handled under these conditions suggests that it will soon be the subject of chemical as well as physical study. The H NMR spectrum (acetone-dg) displays the AA BB system expected for the aromatic protons at 7.82 and 8.28 ppm while the C data show the quaternary carbons at 154.90 ppm (C=0) (cyclo-propenone 155.1 ppm) and 139.33 (Cda/s )). The non-equivalent methine signals resonate at 117.89 and 141.72 ppm and have been assigned to C0/4) amd C(2/s), respectively. These last assignments, made by comparison with cyclobutabenzene-l,2-dione and not verified, run counter to the expectation that of the cycloproparene are influenced... 

Thermal extrusion at 150 °C of carbon monoxide from bis(trichlorovinyl)-cyclo-propenone gives bis(trichlorovinyl)acetylene in 94% yield . Flash-vacuum pyrolysis... 

The pressure-promoted [4 + 2]-cycloaddition of 2-pyrone 318 with cyclo-propenone ketal 377 (25 C, 6.2 kbar) affords a mixture of reaction products exo-adduct 378a, cycloheptatrienone ketal 379, and cycloheptatrienone 380 (resulting from Si02 hydrolysis of 379), each representing the product derived from the Diels-Alder reaction of 2-pyrone 318 with cyclopropen-one ketal 377 (86JA6695). The mdo-adduct 378b loses carbon dioxide upon depressurization, while the exo-adduct 378a is thermally stable. 3-... 

Dichlorocarbene usually undergoes addition to the double bond of enynes in the case of poly-enynes the more substituted double bond reacts faster. Which double bond is attacked also depends on the type of the substituents. Using excess carbene precursor, dichlorocarbene can also undergo addition to the triple bond. The products thus formed are hydrolyzed into cyclo-propenones, either under the reaction conditions or during the workup of the reaction mixture. In separate instances, exclusive addition of dichlorocarbene to the triple bond of enyne was observed (Houben-Weyl, Vol.4/3, pp 172-175 and Vol.E19b, ppl543-1544). 

Divinylcyclopropanes of type 2 are generated by functionalization of masked cyclo-propenones. In the presence of a catalytic amount of tetrakis(triphenylphosphane)palladium(0), cycloheptadiene 3 was obtained directly. 

Electrophilic aromatic sustitution of phenylcyclopropenones occurs at the meta positions. Nitration of 2,3-diphenylcyclopropenone with an equimolar amount of sodium nitrate in concentrated sulfuric acid at 20 to 100°C gave 2-(3-nitrophenyl)-3-phenylcyclopropenone in 49% yield, and with two molar equivalents of sodium nitrate gave 2,3-bis(3-nitrophenyl)cyclo-propenone in 35% yield. 

Cyclopropenones reacted with iran -carbonylbis(triphcnylphosphane)rhodium trifluoro-methanesulfonate at 20 C to give the cationic complexes 4. In these compounds, the cyclo-propenone is bound to rhodium through the oxygen atom without opening of the three-mem-bered ring. ... 

Acyl and sulphonyl isocyanates react with diphenylcyclopropenone, presumably via initial attack on the ketone group, providing cyclo-propenone imines [197] ... 

Cyclopropeneimonium salts have been made by reaction of cyclo-propenones with substituted ammonium salts [156] or of ethoxycyclo-propenium salts with amines [157]. Evidence that the positive charge is not located solely on the nitrogen atom as in [VA) but is shared with the cyclopropene ring as in (VB] comes from variable temperaturen.m.r. studies, which show that rotation about the carbon-nitrogen double bond is easier than in acyclic imonium salts [156]. 

Cyclopropene shows an endo selectivity in its Diels-Alder reactions with the tropylium ion, cyclopentene, and acenaphthene because of Ti-alkyl interactions. " Hoffmann calculations show that in the Diels-Alder reaction of butadiene and cyclo-propenone the two reactants do not approach each other in parallel planes. ... 

Simple Diels-Alder Additions.—The [4 + 2] and reverse-[4 + 2] cycloaddition reactions of species containing C=X bonds (X = P, As, Sb, Bi, Si, Ge, etc.) have been discussed and the evidence reviewed.The general chemical reactivities of cyclo-propenones and triafulvenes, including their behaviour in Diels-Alder reactions, have been broadly summarized. Kagi and Johnson have reported extensive studies on the Diels-Alder reactions between cyclopropene and various chloro-cyclopentadienes in which endo-adducts are obtained, selective dechlorination, hydrolysis and other reactions of these adducts, and H n.m.r. spectral correlations. 

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