Cyclopropanol oxidative cleavage

Alkyl substituted cyclopropanols and cyclopropanone hemiacetals 115,116a) aiso undergo oxidative cleavage when exposed to air or peroxides the initial products are hydroperoxides such as 148. In the case of l-methoxy-2,2-dimethylcyclopropanol, the reaction can be followed by observing the emission peaks in the NMR spectrum, and these CIDNP effects have enabled identification of radical intermediates.1154) With di-f-butylperoxylate (TBPO), the isomeric radicals 143 and 144 are formed and these may undergo a diverse number of further reactions as indicated by the complex product mixture given in Table 20. 

An approach to a prostaglandin intermediate employed a cyclopropanol oxidation with a mixed chro-mate/cerate reagent shown in equation (26), but the yield was unacceptably low. Although no information on the selectivity is available, the trans stereochemistry of oxidative cleavage in the reported product is of note. In these more complex substrates, side reactions and low yields plague the reaction, which will see only limited use in synthesis unless a better reagent system is developed. 

Cyclopropanols and therefore cyclopropanone hemiketals are particularly sensitive to oxidative cleavage. The latter undergo oxidative cleavage of the C(l>-C(2) bond leading for the most part, to jS-propionate radicals which then may undergo a variety of second-stage conversions, as summarized in Scheme 23. With air or peroxides, hydroperoxides (50) are formed (equation 29). 

Oxidative cleavage of the l,2-bis(siloxy)cyclopropane 8 with aqueous sodium periodate similarly affords 1,3-dione 9, in this case in 37% yield.Upon treatment with iron(III) chloride, 1 -(methylsulfanyl)cyclopropanol undergoes a similar chlorination with ring opening to give a / -chlorinated thioester. ... 

Oxidative Cleavage, Full details on the oxidation of cyclopropanols by chromic acid have now appeared. ... 

Cyclopropanol (Schaafsma et al., 1966) and cyclobutanol (Meyer and Rocek, 1972) undergo rapid oxidative cleavage, due to the release of the strain energy of the aliphatic ring. Chain opening is a typical reaction of strained cycloalkanols in presence of one-electron oxidants. A mixture of reaction products is formed, and the actual composition of the reaction... 

Another example is the asymmetric synthesis of ( )-pinidine 208 and its isomers. These syntheses are achieved via asymmetric enolization, stereoselective cyclopropanation, and oxidative ring cleavage of the resulting cyclopropanol system (Scheme 5-68).123... 

Oxidative opening of siloxycyclopropanes. Tertiary cyclopropanol systems undergo ring cleavage with a catalytic amount of VOfacaclj under oxygen to furnish 3-hydroxy ketones and 3-diketones. 

Cyclopropanol cleavage. 1-Substituted cyclopropanols undergoes oxidative opening to afford l-alken-3-ones. Although many other Pd reagents are also useful for this transformation, PdClj without phosphine ligand is an exception. 

Cleavage of l-trimethyhilyloxybicyclo[n.l.O]alkanes. These cyclopropane derivatives (I) are cleaved by LTA in glacial acetic acid to acyclic oi-unsaturated carboxylic acids (equation I). An intermediate cyclopropanol (o) is formed initially and then two bonds of the cyclopropane ring are cleaved by oxidation. ... 

This transformation was proposed to proceed via the pathway shown in Scheme 17.11 [14b]. l-(l,2-Propa-dienyl)cyclopropanols (as exemplified by the reaction of compound 47) reacts with Co2(CO)g to give the carbonyl inserted intermediate 51, which undergoes cyclopropane cleavage to give a metallacyclic intermediate 52. Reductive elimination transforms 52 to cyclohexenedione 53. Then 53 readily tautomerizes to hydroquinone 49, which is readily further oxidized to benzoquinone 50 by air. Hydroquinone 49 can be trapped by acetic anhydride to give 48, or can be... 

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