Chromium (VI) adsorbed on SiO2/ZrO2, a new supported reagent for allylic oxidations

Baptistella, Lúcia Helena Brito; Sousa, Ilza Maria de Oliveira; Gushikem, Yoshitaka; Aleixo, Adriana Mendes

doi:10.1016/s0040-4039(99)00335-4

Cited by 18 publications

(5 citation statements)

References 22 publications

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“…Baptistella et al reported that chromium(VI) adsorbed on silica/zirconium(IV) oxide with tert-butyl hydroperoxide as a cooxidant was an effective system for the allylic oxidation of various cyclic olefins. 97 As depicted in Scheme 15, (+)limonene (27) and 70 were oxidized regioselectively to the corresponding enones 29 and 71, reflecting the low reactivity of exocyclic double bonds that was mentioned earlier.…”

Section: Chromium On Solid Supportmentioning

confidence: 84%

Allylic Oxidations of Olefins to Enones

Weidmann

Maison

2013

Synthesis

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Allylic oxidations of olefins to enones are C-H functionalizations and are valuable organic transformations that permit the synthesis of value-added products from simple precursors. A variety of stoichiometric and catalytic metal-based methods are available for these conversions. In addition, metal-free and biocatalytic protocols are gaining in importance. This review summarizes the available oxidation methods and compares their regio-and chemoselectivities.

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Section: Chromium On Solid Supportmentioning

confidence: 84%

Allylic Oxidations of Olefins to Enones

Weidmann

Maison

2013

Synthesis

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“…Indeed, tert-butoxide and tert-butyl peroxy radicals are formed through degradation of TBHP by catalysts. Those radicals then oxidize steroidal compounds [19,20,[26][27][28][29][30][31][32][33]36].…”

Section: Reported Methodsmentioning

confidence: 99%

A Short Review of Methods for the Allylic Oxidation of Δ5 Steroidal Compounds to Enones

Sg¹,

Jp²

2016

J Steroids Horm Sci

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Introduction of α, β-unsaturated ketones to ∆ 5 steroidal olefins changes the characteristics and biological function of those compounds. Several synthetic methods have been reported to accomplish carbonyl introduction to ∆ 5 steroidal olefins. Herein, this short review will catalogue many of those oxidative methods, particularly those proceeding through a peroxide intermediate and/or use chromium complexes as reagents. to undesired side products, one in particular being C25 for steroids with side chains [15]. Furthermore, cleavage of the side chain can occur concurrent with allylic oxidation [16].Protecting the C3 hydroxy group is commonly accomplish by esterification using acetic anhydride to make cholesteryl acetate. The authors of this review prefer esterification with benzoyl chloride since cholesteryl benzoate products can be more easily isolated with recrystallization in acetone and water than the steroidal acetates. This esterification is necessary because many oxidants and catalysts will convert the C3 hydroxyl group to a ketone [17].Due to interest in "green" or environmentally benign chemistry, chemists have questioned the ethics of earlier catalysts. Environmental and health concerns have motivated the search for new oxidants and catalysts [18]. From chromium based catalysts, the next phase in steroidal allylic oxidation manifested through more environmentally friendly metallic catalysts that use TBHP as an oxygen donor. Meanwhile, several methods have been reported to give steroidal oxidation without any metal catalysts using as sodium chlorite and sodium hypochlorite [19,20]. Additionally, recoverable heterogeneous catalysts, clay

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“…Moreover, we could find in the literature only a few reports on the catalytic oxidation of α-bisabolol in general, with all the studies using hydrogen peroxide or peroxo compounds as final oxidants to obtain bisabolol oxides or allylic ketones. 34,35 All bisabolane derivatives obtained in the present work are novel compounds and are potentially useful for cosmetic and pharmaceutical applications.…”

Section: Introductionmentioning

confidence: 94%