Synthesis of α,β-Epoxy Ketones from Alkyl- and Arylsubstituted Cyclopropanols

Abstract

A number of aliphatic and arylaliphatic a,b-epoxy ketones were prepared in good yields in a one-pot procedure by a manganese-catalyzed ring cleavage of 1-substituted and 1,2disubstituted cyclopropanols with oxygen followed by dehydration of the resulting cyclic peroxides with alkali.

Rearrangements of organic peroxides and related processes

“…The base-catalyzed rearrangement of cyclic peroxides 488a–g , which are prepared by the manganese-catalyzed oxidation of 1- and 1,2-disubstituted cyclopropanols 487a–g , provides a convenient approach to the synthesis of aliphatic and arylaliphatic α,β-epoxy ketones 489a–g . The latter compounds are attractive substrates for the synthesis of for example natural compounds ( Scheme 140 ) [ 459 ].…”

Facile Conversion of Cyclopropanols into Linear Conjugate Enones

“…Nevertheless, it still seems to us that interaction of Co(acac) 2 with O 2 and cyclopropanol may result in oxygen‐centred radical species (see below), with or without added Et 3 SiH, and thus may initiate subsequent reactions in a manner similar to those in Kulinkovich's10 conversion of cyclopropanols into linear epoxy ketones mediated by Mn II abietate (in which the hydroperoxy intermediate reacted with the carbanion generated at the carbon α to the ketone carbonyl group by treatment with KOH).…”

A convenient route to 1-(2-oxiranyl)-1,4-diketones and their application to the synthesis of endo-brevicomin, endo-isobrevicomin, frontalin and related compounds via alkylated 6,8-dioxabicyclo[3.2.1]octan-2-ones

“…11 The Mn(II) abietate catalyzed oxidative cleavage of compounds 3a,b with molecular oxygen, followed by treatment of the reaction mixture with aqueous potassium hydroxide, led to the expected products 4a,b, wich exhibit a trans-configuration of the oxirane ring. 9 The synthesis of compound 4c started with the cyclopropanol 3c, prepared from the protected ethyl levulinate 2a and propylmagnesium bromide. Compound 3c was subjected to the reaction with the bromine -pyridine complex, followed by dehydrobromination of resulting b-bromoketone.…”

“…3 Recently, we have reported a flexible and convenient method for the preparation of aliphatic a,b-epoxyketones based on a manganese-catalyzed ring cleavage of 1-substituted and 1,2-disubstituted cyclopropanols with gaseous oxygen followed by transformation of the hydroperoxyketone intermediates into the target products, under the action of potassium hydroxide. 9 The simplicity of this one-pot procedure, coupled with facile availability of the corresponding cyclopropanols, 10,11 makes it attractive for the synthesis of epoxyketones bearing an additional functional group in the aliphatic chain. In the present work, we wish to describe the application of this methodology to the preparation of 1-(2-oxiranyl)-1,4-diketones 6, which are then employed in the synthesis of 6,8-dioxabicyclo[3.2.1]octane derivatives, including (^)-endo-brevicomin 1b, (^)-endo-isobrevicomin 1d, (^)-frontalin 1e and the related hydroxy compounds 8a, 9a.…”