Allylic aromatic compounds

Base-catalyzed Isomerization of Allylic Aromatic Compounds [68]... 

We have further examined the reactions of thiolato-bridged diruthenium complexes with other unsaturated organic substrates. When the cationic Ru complex 4 is treated with cinnamyl alcohol in p-xylene, the allylated aromatic compound 18 is obtained in good yield (Equation 6). We assume a Tc-allyl intermediate because the reaction using l-phenylprop-2-en-l-ol gives, instead of cinnamyl alcohol, the same product 18 however, the detailed reaction mechanism is still obscure. This novel allylation reaction is halogen-free, and may replace the conventional Friedel-Crafts alkylation. 

Ether groups in the benzene ring of quinazoline behave as in ethers of homocyclic aromatic compounds, e.g., they can be demethylated with anhydrous aluminum chloride. Allyl ethers also undergo a Claisen rearrangement/ ... 

Even fully substituted aromatic compounds can be prepared utilizing the Mi-chael/Dieckmann strategy. As reported by Covarrubias-Zuniga and coworkers (Scheme 2.32) [67], reaction of the anion of l-allyl-l,3-acetonedicarboxylate (2-138) and the ynal 2-139 afforded the intermediate 2-140 which led to the resorcinol 2-142 with spontaneous aromatization under acidic conditions via 2-141 in an overall yield of 32 %. 2-142 was transformed into mycophenolic acid (2-143) in only a few additional steps [68]. 

Whatever the best explanation may be, an indication that allylic alkali metal compounds or allylic carbanions do in fact form the less stable of the two possible acids on neutralization is found in the results of the reduction of aromatic compounds by dissolving metals.376The detection of a paramagnetic intermediate in a similar system and polaro-graphic evidence indicate a one electron transfer in the rate and potential determining step.878 376 The mechanism therefore involves ions (or organometallic intermediates) like the following ... 

Since NBS is conveniently handled and since it is unreactive towards a variety of other functional groups, it is a valuable reagent for brominating in allylic position in olefines, acetylenes or even aromatic compounds. 

Prenyltransferases are a class of enzymes that transfer allylic prenyl groups to acceptor molecules. Prenyl transferases commonly refer to prenyl diphosphate synthases (even though the class of prenyl transferases also includes enzymes that catalyze the transfer of prenyl groups to acceptors that include not only isopentenyl diphosphate (IPP) but also aromatic compounds and proteins etc.). 

A number of gem-dibromocyclopropane derivatives has been reacted with aromatic compounds in the presence of aluminum chloride or ferric chloride providing indenes in yields up to 80%. To rationalize this interesting anellation process it has been proposed that the cyclopropyl cation formed under the influence of the Lewis acid collapses to an allylic ion, which then functions as the alkylating agent [179],... 

A nucleophilic mechanism can be applied in reductions with complex hydrides of highly fluori-nated aliphatic and alicyclic fluoroalkenes with electron-deficient C = C bonds the hydride anion adds as a strong nucleophilic agent to the more electrophilic carbon atom the intermediate anion can then lose a fluoride ion either from the original C = C bond, or from the allylic position finishing an SN2 displacement of the fluorine. Thus, the reductions of vinylic C-F bonds with hydrides proceed by a nucleophilic addition-elimination mechanism. Displacement of fluorine in highly fluorinated aromatic compounds proceeds by the same mechanism ... 

The oxidative carbonylation of arenes to aromatic acids is a useful reaction which can be performed in the presence of Wacker-type palladium catalysts (equation 176). The stoichiometric reaction of Pd(OAc)2 with various aromatic compounds such as benzene, toluene or anisole at 100 °C in the presence of CO gives aromatic acids in low to fair yields.446 This reaction is thought to proceed via CO insertion between a palladium-carbon (arene) allyl chloride, but substantial amounts of phenol and coupling by-products are formed.447... 

Normal alkenes—which are particularly not electron-rich—are oxidized at the allylic position by PCC, resulting in the formation of enones.264 Aromatic compounds suffer a similar reaction at the benzylic positions, yielding aromatic ketones265 or aromatic aldehydes.266 These oxidations normally demand quite harsh conditions with excess of PCC, long reaction times and high temperature. Therefore, they hardly compete with the oxidation of alcohols, which is normally made under quite mild conditions. 

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