Oct-2-enonate

Ethyl 2,3-dideoxy-D-g(uco-oct-2-enonate pentaacetate (86a) (Refs. 4, 5, 21, 25, 39 and 63) and its D-galacto analog (86b) (Refs. 25, 39, and 63) were reportedly obtained starting from aldehydo-D-g ucose and aldehydo-Tt-g l ctose pentaacetates. Syntheses of ethyl 2,3-di-... 

It was also of interest to synthesize derivatives of a,/3-unsaturated acids by using modified alkoxycarbonylmethylenetriphenylphos-phoranes, Ph3P=CHXC02R. This approach led to synthesis of ethyl 2,3-dideoxy-2-phenyl-D-gluco-oct-2-enonate 4,5,6,7,8-pentaacetate25... 

A Wittig reaction on aldehydo-2,4 5 6-tetra-0-methyl-D-glucose gave the -oct-2-enonic acid derivative (21), which yielded the lactone (22), an Intermediate for synthesizing octoses. Wittig... 

Cyclohept-2-enone and cyclo-oct-2-enone undergo ring-contraction to 1-acetyl-cyclopentene and 1-acetylcyclohexene, respectively, in aqueous ethanol containing triethylamine at 140 Treatment of eucarvone with sodium hydride and methyl iodide gave a mixture of products including the bicyclic compounds 3-methylcar-4-en-2-one and l,3-dimethylcar-4-en-2-one. Attempts to dehydrate cycloheptene (237) gave mixtures of dimethylisopropylbenzenes. ... 

Cyclo-octa-1,3-diene is obtained by heating 8,8-di-iodobicyclo[5,l,0]octane in quinoline at 155°C. Treatment of l-trimethylsilyloxybicyclo[5,l,0]octane with iron(iii) chloride and sodium acetate gave cis-cyclo-oct-2-enone (92 %). °... 

Direct photoisomerization of cyclo-octene gives a trans. cis ratio of 49 51, respectively, in the photostationary state, whereas photostationary trans cis ratios of 5 95 and 13 87, were observed on toluene photosensitization in the liquid and vapour phases, respectively. On irradiation, mixtures of isoprene and either cis-cyclohept- or cis-cyclo-oct-2-enone give the Diels-Alder adduct of the trans-cyclo-alkene similar Diels-Alder adducts were obtained using cyclopentadiene. ... 

Oxymercuration-demercuration of 5,6-epoxy- and 4,5-epoxy-cyclo-octenes leads largely to CTido-9-oxabicyclo[3.3 l]nonan-2-ol. Cyclo-oct-4-enone and cyclo-oct-2-enone give largely hydroxy-ketones, whereas cyclo-oct-3-enone... 

Cyclic Ketones.—Protonation of cyclohept-2-enone or cyclo-oct-2-enone at low temperature produces two stereoisomers of the form (322) and (323), where n = 1 or 2, respectively. ... 

In the Weiss reaction (Scheme 4), an 7-dicarbonyl compound (38) condenses with two molecules of dimethyl 3-oxoglutarate (39 E = CC Me) to give a c w-bicyclo [3.3.0] oct-ane-3,7-dione tetraester (40) the one-pot reaction produces considerable complexity, with the sequential formation of four C—C bonds. Simple acid treatment removes the carbomethoxy groups, if deshed. While die reaction involves aldol and Michael sequences, die intermediacy of a cyclopentenone [4-hydroxycyclopent-2-enone (41)] has up to now been unproven. A series of such 1 1 adducts has now been reported for a variety of diketones, together with evidence diat diey are indeed intermediates en route to the bicyclo system.62 Electronic and steric effects on the reaction are also discussed in detail. 

N.m.r. data for several unsaturated ketones and the corresponding alkenes, saturated ketones, and alkanes, have been analysed in terms of n-electron densities. Included are data for cyclohepta-2,7-dienone, cyclo-octa-2,4-dienone, cyclohept-2-enone, cyclo-oct-2-ene, and tropone. The n.m.r. spectra of several di-esters, including medium-ring examples, have been reported. Boron trifluoride complexa-tion of cycloalkanones has been studied using n.m.r. at low temperatures (— 85 to —125 °C) separate signals for both the complexed ( 24 p.p.m. downfield) and free ketones were observed. ... 

Cyclo-octa-2,4-dien-l-ol is converted into anti -2,3-epoxycyclo-oct-4-enol (91 %) on treatment with m-chloroperoxybenzoic acid, whereas t-butyl peroxide-VO(acac)2 gives the bicyclic ether (163 78 %). 2,6,6-Trimethylcyclohepta-2,4-dienol is converted into syn-2,3-epoxy-2,6,6-trimethylcyclohept-4-enol (65 %) by m-chloroperoxybenzoic acid and into (164 86%) by t-butyl per oxide-VO(acac)2- As the syn-epoxycyclo-heptenol gave (164) on treatment with VO(acac)2, it was suggested that in the t-butyl peroxide-VO(acac)2 epoxidations the bicyclic ethers were formed via the syn-2,3-epoxides and subsequent transannular S 2 substitution. The nature of the products obtained from reactions of epoxides with lithium diethylamide is solvent dependent. Thus the mono-epoxide of cyclo-octa-1,5-diene gives cyclo-oct-3-enone in benzene or ether and bicyclo[5,l,0]oct-2-en-syn-6-ol in HMPT the exocyclic... 

When di-p-chloro- and di-p-methoxidobis(2-methoxycyclo-oct-5-enyI)dipallad-ium(ii) were refluxed in methanol with and without added base, and when dichloro-(cyclo-octa-l,5-diene)palladium(ii) was refluxed in methanol with added base, complex mixtures of products were obtained comprising cyclo-oct-4-enyl methyl ether, cyclo-oct-4-enone, and cyclo-octa-2,4-, -2,5-, -3,5-, and -1,5-dienyl methyl ethers. 

Addition took place when the enone (49) was treated with the thiolane anion (50) to give the j8-product (51) as well as an isomer with inverted stereochemistry at C-4 and C-1. The A -ray analysis of this latter product was carried out, and from the two products four isomeric oct-2-ulose derivatives, e.g. (52), were obtained. ... 

The Baeyer-Villiger oxidation of l-methoxybicyclo[2.2.2]oct-5-enones, which are easily prepared by hydrolysis of the Diels-Alder adducts derived from dihydroanisoles and a-chloroacrylonitrile, provides an attractive route to 4-substituted cyclohex-2-en-l-one 4-acetic acid derivatives (Scheme 17)/ Substituted cyclohexenes of the type (124) are produced under mild conditions and in good yield by Claisen rearrangement of mixed ketene-acetals derived from the substituted lactone (123)." ... 

An examination of the phosphorescence spectra and lifetimes of Py-un-saturated ketones, including 2,2-dimethylcyclohept-3-enone and cyclo-oct-3-enone. suggests n-iz triplet excited states. ... 

A simple example from the first report of this reaction by Gilbert Stork and his group in 1974 is the condensation of pentan-2-one with butanal to give the aldol and then the enone oct-4-en-3-one by acid-catalysed dehydration. The yields may seem disappointing, but this was the first time anyone had carried out a crossed aldol reaction like this with an unsymmetrical ketone and an enolizable aldehyde and got just one aldol product in any reasonable yield at all. 

The Oxa Di-n-methane Reaction and Related Processes - A detailed examination of the triplet and singlet state reactions of a series of P,y-unsaturated enones has been reported. Many examples are cited and are typified by the conversion of the enone (140) into (141) on sensitized irradiation. This reaction is a typical example of the well known oxa-di-n-methane process, which fundamentally involves a 1,2-migration of the acyl group. Direct irradiation populates the singlet state of the enone (140) and this yields (142) by a 1,3-acyl migration. The oxa-di-n-methane reaction of chiral bicyclo[2.2.2]oct-5-en-2-one systems has been used as a path to tricyclic ketones. 

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