2-chloro-tropone

Tropone (125) and the 2-substituted tropones showed a different reactivity in the cycloaddition with 2-cyclopentenone (28). Whereas tropone itself (125) and the 2-methoxytropone (126) reacted at lOkbar, giving a mixture of four and three products, respectively (Scheme 5.18), 2-hydroxy- and 2-chloro-tropone failed to react at all [43b]. Compound 127 does not have the expected dihydro-homobarrelenone framework it is probably derived from the cycloaddition of 125 and 1,4-cyclopentadien-l-ol, the enol form of 28. 

Interesting highly colored compounds were reported to be prepared by treatment of 2-substituted tropones with thiourea. Thus the orange or yellow 3-aza-l-thiaazulenes 227400,401 are formed from 2-chloro-tropones however, the scarlet diazaazulene 228402 was produced from a 2-methoxytropone under the influence of sodium ethoxide. 

Another versatile two-step synthesis of homobarrelenones [45] is based on the high pressure cycloaddition of tropone (125) and its 2-methoxy-, 2-hydroxy- and 2-chloro-derivatives with 2,3-bis(methoxycarbonyl)-7-oxabicyclo[2.2. l]hepta 2,5-diene (133) followed by thermolysis of the cycloadducts at 130 °C with the... 

All the bridged [1 ljannulenones condense with malondinitrile in acetic anhydride and yield the corresponding dicyanomethanohendecafulvenes (e.g. 11 - 38) and these on treatment with strong acid furnish the substituted l,6-methano[ll]an-nulenium ions. 11 -Chloro-3,8-methano[ 11 Jannulenone 31, in parallel with the behaviour of the similarly 2-substituted tropone, undergoes reaction with sodium meth-oxide at room temperature to afford chiefly the products of normal 39 and cine substitution 40. 

Ring expansion of cycloproparenes to cycloheptatrienes or tropones has been discussed in the context of electrophilic addition to cycloproparenes. When 1,1 -di-chloro-2,5-diphenylbenzocyclopropene (22) is thermolyzed in refluxing benzene, the dimer 373 is formed as a mixture of /Z-isomers. It is believed to arise via dimerization of the carbene 372, which, in turn results from an allylic rearrangement of22to371. ... 

The halogenation of benzothiazinotropones 361 and 362 as depicted in Scheme 97 affords 7- and/or 9-substituted derivatives like 363 and 364 (66BCJ1980). Chlorination of 362 additionally gives the 9-chloro compound or, on treating the tropone with thionyl chloride in excess (2.5 molar equivalents), a 7,9,Jc-trichloro derivative, presumably substituted at the benzene ring. 

Suitably substituted tropylium salts offer an alternative to condensation with active methylene compounds (cf. Section IV,A,4,c) even if the application of tropones fails. Thus, 6-chloro derivative 266c (82CB3756) or thioether 605 (Scheme 163 91KGS1432) were used to get, respectively, sesquifulvalenes and heptafulvene 606. O-Functionalized compounds are likewise applicable (Scheme 110 cf. 73CRV293, p. 308). 

Chloro-substituted derivatives 11 and 13 of tropones were prepared in good yields by solvolysis of tetrachlorobicyclo[4.1.0]heptenes 10 and 12, which were obtained in moderate yields by Diels-Alder reaction of tetrachlorocyclopropene with electron-rich 1,3-dienes. ... 

Chlorotropone reacts with nitric acid to give 2-chloro-7-nitro-tropone with dinitrogen tetroxide some dinitration [at C(4)] also takes place. With either reagent some benzenoid products, formed by rearrangement reactions, are also obtained. 

Dicyanoheptafulvene has been made from tropyliom bromide [359], tropone [369] or alkoxy- [94,369] or chloro-tropylium salts [370], and malononitrile. It is a stable red solid and does not react with dienophiles or with electrophiles under normal conditions. It will, however, add bromine under the influence of light [371]. 

Tropone allowed to react with phosgene or oxalyl chloride, the resulting chloro-tropylium chloride dissolved in acetic anhydride, ice-cooled, and treated dropwise with the equimolar amount of 70%-HC104 dilorotropylium perchlorate (Y 80-90%) stirred 2 hrs. at room temp, with excess dry isopropanol -> isopropoxy-tropylium perchlorate (Y 81%). F. e., also substitution with mercaptans and amines, s. E. Haug and B. Fohlisch, Z. Naturf. 24b, 1353 (1969). 

Tropone radical anion was formed by electrolytic reduction of 2-iodo-, 2-bromo-, and 3-chlorotropone, but not by electrolytic reduction of 2-chloro- or 2-fluoro-tropone. The anion radicals of 5-nitro-, 3-nitro-, and 3,5-dinitro-tropolonates, and of 2-methoxy-5-nitrotropone have been generated electrolytically in DMF and their e.s.r. spectra studied. The results obtained for 3-nitro- and 3,5-dinitro-tropolonates suggested that the 3-nitro-groups are twisted by 40° and 55°, respectively, from the plane of the ring. ... 

Six membered Rings.— The cycloadducts (277) are formed in good yield by reaction of sulphene with open-chain enaminones bearing a phenyl group at the 2-position.The conversion of 2-chloro-oxirans to 6-membered heterocycles has been described. The reaction with bidentate nucleophiles is most interesting, leading to mixed heterocycles such as (278). Tropone also reacts with 2-mercapto-ethanol to give a 95 5 mixture of the cyclohepta[l,2-6]-l,4-oxathiins (279), which could be separated by h.p.l.c. 

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