706. Molecular rearrangement and fission of ethers by alkaline reagents

Abstract

Under the influence of an alkaline reagent, an ether having a mobile proton may undergo rearrangement (a) or fission (b) :The incidence of these reactions has been examined for phenacyl, 9fluorenyl, and a-cyanobenzyl ethers in butanolic sodium butoxide. But-2-enyl, l-methylallyl, and active a-methylbenzyl ethers of fluoren-9-01 showed unexpected behaviour.THE rearrangement of ethers, CHR,-OR' ---f CR,R'-OH, under energetic alkaline conditions has been recorded by Schorigin and investigated extensively by Wittig2 H a ~s e r , ~ and Curtin and their collaborators. This change is often accompanied or superseded by a process of fission according to the more detailed scheme:Cram, Kingsbury, and Langemann have examined this process of fission in some detail.The main driving force for the rearrangement is no doubt the transference of the formal charge from carbon to the more electronegative oxygen atom; rearrangement of tertiary amines, in which 0 in the scheme is replaced by NR", takes place much less readily (following paper) ; rearrangement of quaternary ammonium compounds : CHRz*&R"2R' __f CR2-GR"2R' + CR2R'.NR''2

Applications of the Wittig–Still Rearrangement in Organic Synthesis

“…[9] Cast and Stevens reported the first confirmed example of a [2,3]-rearrangement in 1960. [10] Thetreatment of either 13 or 14 led to compound 15,bya [1,2]-rearrangement in 13 or a [2,3]-rearrangement in 14 (Scheme 3C).…”

“…[9] C) The first confirmed [2,3]-rearrangement of 14 leading to the homoallylic alcohol 15. [10] several recent reviews on Wittig rearrangements, [15,16] including one on the [1,2]-Wittig rearrangement. [17] Heteroatom variants of the Wittig-Still rearrangement have also been developed, including thia-(Scheme 5A) [11f] and aza-(Scheme 5B) [18] versions.…”

Reactivity of Carbenes and Related Compounds towards Molecular Nitrogen

“…Attempted Preparation of 9-fFluorou1koxy)fluorene.~ from 9-Bromofluorene. Following the method described [53] for the synthesis of 9-alkoxyfluorenes from 9-bromofluorene and silver salts in alcoholic soln., the preparation of 9-(hexafluoroisopropoxy)fluorene and 9-(trifluoroethoxy)fluorene was examined in analogous reactions in HFIP and TFE, respectively. A soh.…”

Preparation of aryl benzyl ketones by [1,2]-Wittig rearrangement

“…5 Substituted ethers 1, in which G can function as a leaving group as well as an electronwithdrawing group, eliminate group G after [1,2]-Wittig rearrangement to form the carbonyl compounds 3 (Scheme 1). Such reactions have been reported for G = cyano, 6 imidazolium and benzimidazolium 7 groups. α-(Benzotriazol-1-yl)alkyl allyl ethers have been successfully utilized in the synthesis of homoallylic ketones and alcohols via [2,3]-Wittig rearrangements.…”