Acetoxy lation

Strong acids enhance oxidation, and extensive transformation can be achieved at room temperature [see Eq. (9.160)]. In the absence of oxygen, side-chain acetoxy-lation and hydroxylation take place.842... 

Diacetoxy-2-butene. Mitsubishi commercialized a new proces, the acetoxy-lation of 1,3-butadiene, as an alternative to the Reppe (acetylene-formaldehyde) process for the production of l,4-diacetoxy-2-butene. l,4-Diacetoxy-2-butene is tranformed to 1,4-butanediol used in polymer manufacture (polyesters, polyurethanes). Additionally, 1,4-butanediol is converted to tetrahydrofuran, which is an important solvent and also used in polymer synthesis. 

Table 4-1 weighs the positional selectivity of the side-chain cation-radical acetoxy-lation against the side-chain pure radical bromination. 

Several synthetic procedures for the preparation of C-2-acetoxy- and methoxy-cephalosporins have been reported20). The functionalization at the C-2 position of cephalosporin 15 can be started with the oxidation of the divalent sulfur atom which produces sulfenium cation intermediates, which are precursors of C-2-substituted cephalosporins. The electrochemical conversion of cephalosporins 15 into their C-2-substituted homologs has been realized 2,). For example, the electrochemical acetoxy-lation at the C-2 position of desacetoxycephalosporin 15 is carried out in an AcOH— Ba(OAc)2—(Pt) system to give the C-2-acetoxylated products 24 (R1 = CFL,OPh R2 = Me) in 70% yield (Scheme 2-8). Electromethoxylation at the C-2 position of 15 is performed in a MeOH/CHClj—BuEtjNCl—(Pt) system to give the compounds 25 (R1 = CH2OPh R2 = CH2Ph) in 43% yield. The methoxylated product 25 can lead to the further oxidized product 26 by electrolysis in a H20/CHClj—MgC —(Pt) two-layer system. 

Palladium clusters have been reported to catalyze the oxidative acetoxy-lation of alkenes Propene reacts with acetic acid and oxygen to give allyl acetate according to... 

Subsequent acid-catalyzed methoxylation provided two regioisomers 779 and 780 (47 and 39%, respectively). The quinone methide 778 also underwent nucleophilic acetoxy-lation with AcOH-AcONa followed by LiAlHa reduction to afford sinapyl alcohol (781) in 80% overall yield. 

In the early 1970s, our attention was directed to the Wessely acetoxy-lation (13). LTA oxidation of phenolic tetrahydroisoquinolines was exploited in our laboratory to give the corresponding p-quinol acetates, which were proved to be the reactive intermediates for the aporphine synthesis (14-15)-, that is, when an electron-rich benzene ring was present in a given p-quinol acetate, C-C bond formation occurred intramolecu-larly on its acid treatment. 

In Japan, the techniques industrialized employ butadiene. Mitsubishi uses acetoxy-lation, and Toro Soda employs the chlorination of butadiene by the following reactions ... 

Ideally, direct oxidative hydration of 1,3-butadiene is desired rather than acetoxy-lation, but the technical difficulty is very high because water is less reactive compared with acetic acid. 

Starting also from butadiene, Mitsubishi Chemical (29) has developped a process to obtain butanediol by liquid phase acetoxy-lation to 1, ii-diacetoxy-2-butene, followed by hydrogenation and hydrolysis. 

Controlling site selectivity in palladium-catalyzed C—H bond acetoxy-lation of 2-arylpyridines 12ACR936. 

Allylic C-H Bond Activation. Internal alkenes, in particular cyclic ones, can be transformed into allylic acetates in a palladium-catalyzed oxidation (eq 6). With benzoquinone as stoichiometric oxidant or electron transfer mediator, the allylic acetoxy-lation proceeds with high selectivity for the allylic product and usually in excellent yield. 

NATs are also involved in bioactivation reactions via O-acetylation of Y-hydroxylamines formed from CYP-mediated N-hydroxylation of arylamines. These bioactivation reactions form unstable acetoxy esters that decompose to highly reactive species, which bind to cellular DNA [83], The O-sulfonation of compounds catalyzed by SULTs can also result in the formation reactive intermediates. Recently, it has been shown that a-hydroxytamoxifen (derived from CYP-mediated hydroxy-lation of tamoxifen) is bioactivated by SULTs [177],... 

C.i.a. 1,4-Addition of Two Oxygen Nucleophiles. Efficient procedures for 1,4-diacetoxy-lation, 1,4-chloroacetoxylation, and 1,4-dialkoxylation were reported in the 1980s. In the latter reactions nucleophiles were introduced in the 1- and 4-positions.f f f An important issue is to introduce two different nucleophiles in the 1- and 4-positions, respectively. Synthetically useful procedures for the 1,4-acetoxy-trifluoroacetoxylation and 1,4-alkoxy-trifluoroace-toxylation were recently reported (Eqs. 6 and 7). ... 

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