Cyclohepta furan-6-ones

Quaternary ammonium tribromides in methanol-dichloromethane did not brominate the furan ring of 3-methyl-8//-cyclohepta[/>]furan-8-one. Instead, the 7-bromo derivative was formed (92BCJ295). 

On the other hand, the anodic oxidation of 1,3,5-cycloheptatrienes is one of the most powerful key tools for the preparation of a variety of non-benzenoid aromatic compounds such as tropylium salts, tropones, tropolones, 27/-cyclohepta[ ]furan-2-ones and azulenes. ... 

Treatment of the furotropone (105) with the keten (106) leads to the furo-heptafulvalene (107). 2//-Cyclohepta[ )]furan-2-one (108) undergoes twofold [Stt + 27t] cycloaddition to 6,6-dimethylfulvene to yield, after loss of carbon dioxide, the diazulenofulvene (109), accompanied by the rearranged azulenonaphthofulvene (110). ... 

H-Cyclohepta[ ]furan-2-one 478 and related compounds undergo electrophiUc substitutions at the 8-position of the fulvenes [288]. Heteroazulene-substituted tropylium ions 479 are prepared by the reaction of 478 with tropylium ion (Scheme 6.126a) [288]. Nitta and coworkers [289] synthesized ketones 480,... 

Ethynylated 2/f-cyclohepta[()]furan-2-ones 486 are prepared by Pd-catalyzed alkynylation of 3-iodo-5-isopropyl-2//-cyclohepta[ ]furan-2-one 487 with the corresponding ethynylarenes [292]. The compound reacts with tetracyanoethy-lene (TCNE) 488 and TCNQ 25 to afford highly polarized dicyanoethylene derivatives 489 and 490 respectively (Scheme 6.128) [293]. 

H-Benzo[a]carbazole, 4,4a,5,l 1,1 la,l Ib-hexahydro-synthesis, 4, 283 Benzo[b]carbazole, N-acetyl-photochemical rearrangements, 4, 204 Benzo[/]chroman-4-one, 9-hydroxy-2,2-dimethyl-synthesis, 3, 851 Benzochromanones synthesis, 3, 850, 851, 855 Benzochromones synthesis, 3, 821 Benzocinnoline-N-imide ring expansion, 7, 255 Benzocinnolines synthesis, 2, 69, 75 UV, 2, 127 Benzocoumarins synthesis, 3, 810 Benzo[15]crown-5 potassium complex crystal stmcture, 7, 735 sodium complex crystal stmcture, 7, 735 Benzo[ 18]cr own-6 membrane transport and, 7, 756 Benzo[b]cyclohepta[d]furans synthesis, 4, 106 Benzocycloheptathi azoles synthesis, 5, 120... 

Aminopyrans, annulated directly with a seven-membered carbo-cycle, are very rare. One, 139, is formed from substituted cyclohepta[c] furan-4-one 140 with UNs 30 (08CFIE136) (Scheme 50). 

Nomenclature according to Tochtermann et Strictly speaking, compounds of type 368 (X = CO) and 369 should be named from furan as the base system (8Ff-dibenzo[3,4 6,7]-cyclohepta[l,2-c]furan-8-one). 

The PE spectra of 6H-cyclohepta[c]furan-6-one (and molecular orbital calculations on this system) have been reported (84BGJ856). 

Acenaphthylene, indene, and styrene undergo periselective 4 + 2-cycloaddition with 3-ethoxycarbonyl-2//-cyclohepta[Z>]furan-2-one in high yield.152... 

In 5,7-polymethylene derivatives of cyclohepta[c]furan-6-ones, the C=0 band is shifted from 1682 down to 1628 cm1 on lengthening the ansa chain from 7 up to 10 members (85MI3). 

In a unique pathway, cyclohepta[fo]furan-6-ones such as 404a (Scheme 95) first lose CO from the tropone or from the furan rings (94RRC41). 

In the series of heterocyclic fused analogs, Cook et al. (68T4501, 68TL3771) compared the properties of cyclohepta[c]furan-6-one (307a) with those of benzo[d]tropone and tropone by means of HMO calculations, spectra, and chemical reactivity (carbonyl derivatization). Whereas the two fused systems are comparable, their aromatic character is still less than that of tropone. 

The 8 + 2-cycloaddition of 2//-cyclohepta[Z>]furan-2-one (155) with acyclic 1,3-dienes provides a facile route to hicyclo[5.3.0] ring systems (156) (Scheme 61). 2H-Benzo[h]thiete in the o-quinoid form undergoes 8- -2-cycloaddition with 1,3-dithiolane-2-thione, l,3-dithiole-2-thiones, and adamantanethione to produce 4/7-1,3-henzodithianes. ... 

Photocyclisation of 8-alkoxy-l,2,3,4-tetrahydro-l-naphthalenones and 4-alkoxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ones gives naphtho[l, 8-bc]furans and cyclohepta[cd]benzofurans respectively, and conformational and substituent effects of 1,5-biradicals in the cyclisation process are discussed." " The same authors also describe substituent effects on the photocyclisation of ethyl 2-(8-oxo-5,6,7,8-tetrahydro-l-naphthyloxy)acetates and ethyl 2-(5-oxo-6,7,8,9-tet-rahydro-5H-benzocyclohepten-4-yloxy)acetates to give naphtho[l,8-bc]furans and cyclohepta[c,d]benzofurans respectively." Also reported are cyclisations involving photogenerated radical cations of unsaturated silyl enol ethers, fragmentation cyclisations of unsaturated ot-cyclopropyl ketones which occur by photoelectron transfer and give polycyclics, and kinetic and theoretical studies of [2+3] cycloadditions of nitrile ylids. These reactions have been studied mechanistically and their synthetic potential investigated. 

The [8 -I- 2] cycloaddition reactions between substituted cyclohepta[Zi]furan-2-ones and enamines have been described by Kuroda and coworkers pfje cycloaddition reactions proceeded with concomitant elimination of carbon dioxide and amine. Thus, the reaction between 527 and enamine 528 afforded [8 + 2 eyeloadduct 529 with good yield (equation 153) 2c... 

Cinnolinone, 763 Cyclohepta[6]furan-5-one, 1107 Cyclohepia(/>]furan-8-one, 899 Cyclohepta[c)pyrazole, 807 Cyclohepta[c)pyrazol-8-one, 1268 Cycloheptale pyrazolo 1,5-a Ipyrimidine,... 

There are general reviews on heterocyclic syntheses by cycloaddition reactions of isocyanates and on the use of heterocyclic cations in preparative organic chemistry. More specific topics are 5-hydroxymethylfuran-2-carb-aldehyde, isobenzofurans and related ort/io-quinonoid systems, the conversion of 2//-cyclohepta[Zj] furan-2-one (1) into derivatives of azulene, the synthesis of indoles from o-alkylphenyl isocyanides, and abnormal Fischer indolization reactions of o-methoxyphenylhydrazones. Two reviews on isoindoles have appeared and a lecture on highly conducting charge-transfer complexes that are based on heterocyclic selenium and tellurium donors has been reprinted.Recent advances in the chemistry of imidazole and in the use of nitro-imidazoles as radiosensitizers have been summarized. There have been reviews on benzimidazole A -oxides and on dihydrobenzimidazoles, benzimidazolones, benzimidazolethiones, and related compounds. Other topics are synthetic applications of 1,3-dithiolium and 1,3-oxathiolium salts and of isoxazoles, the chemistry of benzisoxazoles, 2-amino-oxazoles, 5-oxazolones (2), furoxans, benzofuroxans, and related systems, the synthesis of five-membered meso-ionic compounds, and tetrazoles. ... 

With active methylene compounds. l-Oxa-2-azulenones (2H-cyclohepta[fc]furan-2-ones) are attacked by carbanions (that are produced from active methylene compounds) at C-8a to yield, after recyclization, bicyclic azulene derivatives (85HOU(5/2c)127, p. 223). In addition, the... 

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