Annelation 18 Annulene

The annelated annulenes 323 and 324 were found to be more weakly diatropic than isobenzofuran. Benzo-annelated bisdehydro[14]annuIenes, 325 and 326 have been prepared by a similar reaction sequence, and found to be moderately and weakly diatropic, respectively. Recently, analogous thiophene and furan derivatives, 327 and 328 have been prepared. Comparison of the H-n.m.r. spectra with... 

The preparation of annelated tetrakisdehydro[18]annulenes 349 and 350 and the reference dehydroannulene 351 afforded further insight into the 7t-electron delocalization in annelated annulenes . When a dihydronaphthalene nucleus in 351 was replaced by naphthalene to form the annelated dehydroannulene 350, an appreciable suppression of diatropicity in 350 was observed. Further replacement of the dihydronaphthalene by naphthalene to give the dinaphtho-annelated derivative 349 resulted in a further suppression of the diatropicity in contrast to the increase of diamagnetic ring current in the case of transition from 342 to 340 and from 343 to 341. 

The Ti —To-value can be regarded as an approximate measure of -electron delocalization in annelated annulene rings. The above-mentioned results obtained on conformationally stable annelated acetylcne-cumulene dehydroannulenes seem to give the following conclusions ... 

Annulyne 82 has been generated from bromide 81 and sodamide, and has been trapped by various furans removal of the oxygen bridge leads to the annelated annulenes. ... 

Naphtho-annelation may cause much less lowering of ring current than benzoannelation, for example, of the following annelated annulenes, the dinaphtho derivative sustains a much greater ring current than the dibenzo derivative, as indicated by the difference in chemical shift between the signals for the inner and. outer protons (Ad = 8.16 for dibenzo, 13.57 for dinaphtho) [261]. It has... 

It has been pointed out, however, that increased diatropicity in these annelated annulenes may go hand in hand with greater sensitivity to air [262]. 

Mitchell RH, Williams RV, Dingle TW (1982) Toward the Understanding of Benz— annelated Annulenes — Synthesis and Properties of [a,h]— and [a,t]—Ring Dibenzannelated Dihydropjrrenes. J Am Chem Soc 104 2560... 

In any other annulene series, if the parent (A) and the benzannulene (BA) are known, then use of eq 15 (modified from eq 10), where AA is the annelated annulene, will provide an estimate for the resonance energy, RE (strictly BLE, see text above), of the annelating fragment of AA. 

The reduction of several annelated corannulene derivatives has been performed using lithium and potassium metals.7 It has been found that annelation affects the annulenic character of corannulene by changing its charge distribution the dianions of derivatives that are annelated with six-membered rings have less annulenic character and are less paratropic than corannulene dianion. 

The properties of annulenes annelated with a 675 ring system are of considerable interest with respect to the participation of benzenoid tt electrons in the macrocyclic Ti-electron system. In the field of dehydroannulenes, a wide variety of annelated derivatives, such as 313314 315316317318 , 319... 

In order to get information on the effect of annelation of a 6tz ring onto macro-cyclic 4 starting material. The reference compound 337 was prepared by the reaction of 334 with maleic anhydride. It was found that the degree of paratropicity decreased in the sequence 337 > 336 > 335 > 333 ci 331. This is the same order as found for the reduction of diatropicity in the annelated bis-dehydro[14]annulenes, 324, 325, 327, 328 and 329. 

Treatment of the cyclic glycol 339, obtained by dimerization of 338, with tin(ii) chloride in THF saturated with hydrogen chloride gave an extremely air-sensitive deep blue-violet solution. Similarly, the non-annelated bis(dihydronaphtho) (341) and the annelated dihydronaphtho-naphtho (342) analogues have been obtained as stable compounds like di-t-butyldiphenylbisdehydro[14]annulene (265b). ... 

The fact that the extremely unstable blue-violet solution gives an electronic spectrum closely related with those of 265a, 341 and 342 indicates the formation of dinaphtho-annelated bisdehydro[14]annulene (340) in the solution. The H-n.m.r. spectrum of 340 can be obtained using a solution prepared with THF-dg and... 

The synthesis and properties of the annelated bisdehydro[18]annulenes, 346 and 347 together with the non-annelated bisdehydroannulene 348 have been... 

Annelation of one or more 6tc electron rings onto a [4n-l-2]annulene ring decreases progressively the diatropicity of the annulene ring provided that the condition in (lY) is not fulfilled. 

Annelation with two 6tc electron rings at positions which make it possible to write equivalent Kekule structures does not suppress the diatropicity of the annulene ring. 

J., Synthesis and properties of a bisdehydro[14]annuleno[c]furan and an ortho-annelated tetrakisde-hydro[ 14]annuleno[ 14]annulene. Bull. Chem. Soc. Jpn., (CI, JH, 1994. 

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