Oxidative oxoester

The cyclic enol ethers 76 either form 1-alkoxy furans 77 by elimination44,1 or, more interestingly, they are oxidized by bromosuccinimide to brominated intermediates 78 which give a,J3-unsaturated y-oxoesters 79 after base treatment45). Reaction of the cyclic orthoesters 76 with LiAlH4 leads to y-oxoaldehydes 80 or their acetals 81 depending on the work-up procedure 46). 

The electrochemical reduction of y-oxoesters like 115, synthesized via the cyclopropane route, results in cyclization with participation of the olefinic unitn>. This reaction provides interesting cyclopentanol derivatives, which can be transformed to the corresponding cyclopentenes. Alternatively a fragmentation to medium sized ketones like 116 occurs after saponification and anodic oxidation 77>. 

TBA-I catalyzed the oxidation of cyclohexane with 1 atm molecular oxygen at 365 K. The main products wa e cyclohexanol and cyclohexanone and an induction period was observed. The selectivities changed little with time. A small amount of dicyclohexyl, which is formed by the reaction of two cyclohexyl radicals, was observed. Neither acids nor oxoesters were observed. The induction period and the formation of dicyclohexyl suggest that the reaction involves a radical-chain autoxidation mechanism. The... 

The new hydrazones were first tested in simple a-alkylation reactions. As is shown in scheme 14, metalation with Lochmann-Schlosser base in THF at low temperature yielded highly reactive azaenolates, which were alkylated by a number of alkyl halides at -100°C in good yields and with high diastereomeric excess (de = 85 - > 95%). It is noteworthy that, besides the usual oxidative cleavage with ozone, the SAMP-hydrazones could be converted without racemization to the final 3-substituted 2-oxoesters under very mild conditions with boron trifluoride-ether in acetone/water with the addition of paraformaldehyde. Thus, this method permitted for the first time the highly enantioselective transfer of a homologous pyruvate unit to electrophiles (scheme 14) [41]. 

Oxoesters are oxidized with Mn(OAc)3 to the corresponding radicals that can add intermolecularly or intramolecularly (eq Ib)" to generate alkyl radicals. In the presence of Cu(OAc)2 the latter are rapidly quenched and oxidized to give alkenes. Radical arylation with alkyl iodides can be induced with dibenzoyl peroxide the yield of the reaction can be improved using a catalytic amount of Cu(0Ac)2-H20, which minimizes hydrogen abstraction by the intermediate radical but introduces a competitive electron-transfer oxidation of the intermediate radical. The oxidative addition of disulfides to alkenes (Trost hydroxysulfenylation ) can be promoted by catalytic amounts ofCu(OAc)2. ... 

---