Alcohols with aromatic rings

Another class of compounds in which irregular Ad signs have been observed is alcohols with aromatic rings in the a-position. This situation is illustrated in Figure 12 by the MTPA esters of the alcohols derived from tautomycin, in which irregular Ad values are found exclusively for the y3-protons (un-... 

Although this method is quite old it has stood the test of time, and is the basis of many modem oxidations with RuO. Sharpless used it for oxidations of alcohols, ethers, aromatic rings and for aUcene cleavage, so clearly it has a high range of applicability. 

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic acids usually occurs with nonspecific oxidants such as KMnO, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(ll) acetate, allyiic and benzylic oxidations are aJso possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian. 1971 A. Friedrich, 1975). 

As expected, the formation of a carbonyl group is not possible with tert-allylic alcohols. Although the aromatic ring bears electron-donating groups, the 2,2-disubstituted chromene 119 was formed smoothly with the tert-allylic alcohol 118[100]. 

Trimelhtate Esters. These materials are produced by the esterification of a range of alcohols with trimeUitic anhydride (TMA), which is similar ia stmcture to phthaHc anhydride with the exception of the third functionaHty (COOH) on the aromatic ring. Consequendy, esters are produced ia the ratio of three moles of alcohol to one mole of anhydride. Common esters ia this family are tris-2-ethyhexyl trimeUitate (trioctyl trimeUitate, TOTM) L79TM, an ester of mixed semilinear C and C alcohols and L810TM, an ester of mixed linear Cg and C q alcohols. 

Sahcyhc acid, upon reaction with amyl alcohol and sodium, reduces to a ring-opened ahphatic dicarboxyhc acid, ie, pimelic acid (eq. 5). The reaction proceeds through the intermediate cyclohexanone-2-carboxyhc acid. This novel reaction involves the fission of the aromatic ring to i j -hexahydrosahcyhc acid when sahcyhc acid is heated to 310°C in an autoclave with strong alkah. Pimelic acid is formed in 35—38% yield and is isolated as the diethyl ester. 

Na, /-BuOH, 70-80°, 2 h, 78%. In this example sodium in /-butyl alcohol cleaves two aiyl benzyl ethers and reduces a double bond that is conjugated with an aromatic ring nonconjugated double bonds are stable. 

Birch reduction (Section 11.11) Reduction of an aromatic ring to a 1,4-cyclohexadiene on treatment with a group I metal (Li, Na, K) and an alcohol in liquid ammonia. 

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