Tropones azulenes

Azulene quinones [49b] are compounds related to the family of tropones and are considered to possess great biological and physiological potential. Several polycyclic compounds have been prepared by high pressure (3kbar, PhCl, 130°C, 15h) Diels-Alder reaction of 3-bromo-l,5-azulene quinone (137) and 3-bromo-l,7-azulene quinone (138) with several dienophiles. The cycloadditions were regioselective and afforded cycloadducts in reasonable to good yields (Scheme 5.20). 

The reaction of carbenoids with aromatic systems was first reported by Buchner and coworkers in the 1890s.6 The reaction offers a direct entry to cycloheptatrienes and has been used to synthesize tropones, tropolones and azulenes.6 Neither the thermal nor copper-catalyzed reactions, however, proceed in good yield. The problems associated with these transformations were clearly demonstrated in a recent reexamination of die thermal decomposition of ethyl diazoacetate in excess anisole (137).129 A careful analysis of the reaction mixture revealed the presence of seven components (138-144) in 34% overall yield (Scheme 29). The cycloheptatrienes (138M142) were considered to be formed by cyclopropanation followed by electrocyclic ring opening of the resulting norcaradienes. A mixture of products arose because the cyclopropanation was not regioselective and, also, the initially formed cycloheptatrienes were labile under the reaction conditions. 

The pKa values given for diphenylcyclopropenone, tropone and azulene-l-aldehyde were obtained by spectrophotometric titration with aqueous acids in the author s laboratory these figures are accurate to 0.3 pK units. The dipole moment of perinaphthenone in benzene was measured by R. J. Best and K. Mead of the Stamford laboratories of the American Cyanamid Co., Connecticut, U.S.A. 

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. ... 

Non-benzoid phanes have always played an important role in cyclophane chemistry and many structures have been prepared with other Hiickel aromatic rings such as azulene or tropone [49]. A cyclophane with two bridged annulene units was recently synthesized by Mitchell [50,51 ]. Dimethyldihydropyrene (76), an excellent NMR probe first introduced by Boekelheide [52], was converted into the dialcohol 77 in three steps. Reaction with adipoyl chloride afforded the large [10.10]cyclophane 78. Unfortunately the conversion of the dialcohol into the corresponding dibromide 79, an obvious precursor to the interesting phane 80, has failed so far. 

The Wittig reaction has been used to construct the side-chain in a synthesis of (-)-sirenin (208), a water mold sperm-attacking hormone.ii The intermediate (206) was generated, without competing formation of the structural isomer (207), by reaction of the ylide (205) with (204) under salt-free conditions in DME. Standard Wittig methods have been used to construct the side-chain in an enantioselective synthesis of (+)-(7 , 9Z)-methyl trisporate (209) and its (9E)-isomer.l 12 The reaction of triphenyl-(vinylimino)phosphorane derivatives (210) with tropones provides a convenient synthesis of 1-aza-azulenes (211) and (212) in either one or two steps (Scheme 28).H The mechanism of the one-step reaction was investigated using deuterium-labelled tropane derivatives. 

Tropone, 1 (a), and azulene, II (a), shown in Fig. 4 have resonance energies, of 12 and 28 kcal/mole, respectively. The theoretical implication of a stable system being achieved by six r-electrons, is that the structures are closer to those shown in I (6) and II (5) certainly this is in keeping with the observed physical and chemical properties. 

For example tropone derivatives have been used as starting materials to obtain various azulene derivatives, [33-36], e,g. 

The acyllactone rearrangement has been simplified by using exchange resins instead of mineral acids as catalysts Extension of this type of rearrangement to acyllactams gives a variety of pyrrolidine and piperidine derivatives related to alkaloids For the preparation of -pyrrolines andzl -piperideines,a new method has been found Easy access to 1-oxa- and 1-aza-azulene derivatives from tropones has been accomplished... 

Fischer indole synthesis to cyclohexanone-2-troponylhydrazone and dehydrogenation of the product to indolo[2,3-h]tropone the 8- and 10-isopropyl-, and 7-bromo-analogues, were also prepared. Treatment of the 2-troponylhydrazones of cyclo-heptanone and JV-benzylpiperidinone with acid gave analogous products. Tndolo[2,3-h]tropone was converted into benzo[h]-l-aza-azulene. ... 

Figure 6.18 Heptafulvene and its polar structure 3, tropone 16, tropolone 447 and azulene 4.

A pioneering study on [6-f4] reactions of diazomethane to dimethylfulvene was reported by Houk [54]. Other advances include the double [6+4] cycloaddition of tropone to dimethylfulvene [55], intramolecular [6+4]cycloadditions of fulvenes [56], selective intramolecular [6+4]cycloadditions of aminodienylfulvenes [57], and the [6+4] cycloadditions of diethylaminobutadiene to fulvenes for the synthesis of azulenes [58]. 

The n.m.r. spectra of a series of 2-substituted tropones have been analysed, using a combination of methods the published assignments for tropolone acetate were corrected and substituent parameters were defined and compared with corresponding parameters for monosubstituted benzenes. Studies of nucleophilic displacement reactions of chlorine or of tosyloxy-groups in troponoids" reveal that with either Mc2NH in DMSO or NaSMe in ethanol, substituents in the 3-position were replaced faster than those in 2- or 4-positions neither M.O. calculations nor e.s.r. studies predicted this. 1,3-Diaza-azulenes are obtained in acceptable yields from the reaction of benzamidine and 2-(ethylthio)tropone in related work, the interesting structure (3) has been recognized. 

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