Synthesis of ketones from substituted ethylenes. Procedure and mechanism

Abstract

A novel method for the direct conversion of some substituted ethylenes to ketones is described. The ketone synthesis is shown to proceed with a concurrent rearrangement of the carbon skeleton. A mechanism, supported by isotopic labeling experiments, is postulated to account for the transformation.The addition of bromine to olefins is a well-known reaction frequently used as a qualitative test for unsaturation.The products of such additions are usually the corresponding dibromides. However, in at least two reported4•5 instances ketones have been isolated as by-products.

C2-Symmetric 1,2-di(fluorenylidene)cyclobutanes: syntheses, structures, rearrangements and reactivity

“…The two ketone groups on C(1) and C(4) adopt an anti orientation and have opposed helicity to the fluorenylidenes. The butadiene unit does not adopt the normally favoured S-trans conformation, presumably as a consequence of the bulky overlapping fluorenylidene Although the synthesis of ketones from substituted ethylenes by treatment with bromine dissolved in methanol has previously been observed by Apelgot 21 and by Curtin,22 and the mechanism was elucidated by Kakis et al, 23 we are unaware of previous reports of the formation of diketones from cycloalkenes, except by use of a strong oxidant such as ozone. One might consider that the direct addition of Br 2 across the PhC]CPh fragment in 21 is sterically hindered, and that instead the reaction proceeds via generation of HOBr mediated by traces of water, possibly during the work-up phase.…”

A Series of Small-Scale, Discovery-Based Organic Laboratory Experiments Illustrating the Concepts of Addition, Substitution, and Rearrangement

“…The crude dichloride, 2, is then transformed into either the corresponding epoxide, 3, (Challenge 1) or into a rearranged ketone, 4, (Challenge 2) via reactions that are promoted by the presence of silver ion and are solvent dependent. The silver ion promoted transformations of vic-dihalides into aldehydes or ketones, a pinacol-like process, is now recognized as the Kakis rearrangement (12,13). Challenge 3 involves the isomerization of the epoxide, 3, to the ketone, 4, using a Lewis acid catalyst (7,14).…”