Jones oxidation side reactions

As the oxidative carbon-carbon bond breakage of alcohols, leading to a stable carbocation, depends not only on the stability of the resulting carbocation but also on very exacting stereoelectronic factors, many cases are known in which alcohols are successfully oxidized to ketones, regardless of apparently easy oxidative carbon-carbon bond breakages. In fact, in synthetic experimental practice, it is recommended not to fail in trying a Jones oxidation because of fear of such side reactions. 

Similar to Jones reagent, Collins reagent can produce a hydroxy directed epoxidation of allylic alcohols. This side-reaction only occurs in a limited number of allylic alcohols, most of them being oxidized uneventfully to the corresponding enones.117... 

Firstly the nitro configuration in compound 1.7.85 was inversed under the base condition. Then the hydroxyl compound was oxidized by Jones antioxidant to afford ketone 1.7.88. After compound 1.7.89 generated from 1.7.88 under Rubottom oxidation, a side reaction was triggered under the hydrogenation conditions and it formed three-member ring product 1.7.90. Although the a-hydroxyl ketone part of compound 1.7.90 could be cleaved by periodic acid and reduced to lactone structure, this synthesis route was not feasible for the total synthesis of natural product. 

The synthesis of PS-5 was achieved by treatment of silylimine of 0-protected (S) lactic aldehyde with the lithium enolate of /-butyl butanoate. The reaction is highly diastereoselective affording almost completely the trans a2etidinone with the natural configuration at C3. This azetidinone was converted, by sequential Jones and Baeyer-Villiger oxidation of hydroxyethyl side chain to the 4-acetoxy doivative that represents a most useful chiral building block fcv the synthesis of final carbapenem PS-5 via the Merck procedure (Scheme 8). 

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