Developing the Scope of O→C Aryl Migrations: Exploring Amide Substrates as Potential Precursors for Asymmetric Reactions

Abstract

A new and mild method for the production of diasteromerically enriched α‐aryl carbonyl compounds has been achieved. Although only modest diastereoselectivies are observed, they demonstrate the potential of the method for further optimisation. It also appears that reactions that proceed through a five‐membered spirocyclic transition state rearrange, whereas those proceeding through a six‐membered transition state do not, but stop at the diaryl ether stage.

The Truce–Smiles rearrangement and related reactions: a review

“…Researchers have typically chosen to prepare an aryl ether substrate by Williamson ether synthesis 30,31,[44][45][46] or an aniline substrate, 47,48 with judicious choice of a base that can subsequently form the carbanion intermediate to instigate the TruceSmiles rearrangement. In one unusual example 43 (Scheme 7), a benzyne intermediate is used to form the sulfonamide bond linking the nucleophilic and electrophilic portions of the substrate 14 with concurrent production of the carbanion nucleophile.…”

“…Many of the numerous substrates [21][22][23]25,26,28,97 studied by the Hirota's research group have been alkyl aryl ethers and the substrates studied by Snape's research group are diaryl ethers. 30,31 The studies that we have published thus far from the Wood research group have exclusively been alkyl aryl ethers. 49 Typically, an acidic aqueous work-up provides the products from these rearrangement products as the appropriate alcohol 58,61 or phenol, [44][45][46]95,96 unless the rearranged alkoxide anion intermediate has been trapped by a tandem reaction, typically cyclization to form a cyclic ethercontaining compound 49 or lactone.…”

“…Examples of Truce-Smiles rearrangements occurring through the formation of 5-membered ring spirocyclic Meisenheimer adducts are most common in the literature, including the reactions reported by Dohmori and colleagues, [8][9][10][11][12][13][14][15] the research groups of Truce, 1-4 Drozd, 16,17 Hirota,18,19,[21][22][23]25,27,97 Snape,31 and Wood, 49 as well as with many other isolated 34,35,41,43,94,[99][100][101][103][104][105]110,112 reactions reported (Fig. 8).…”

“…39 However, reports have started to appear more frequently in the recent literature of stereoselective TruceSmiles rearrangements. 31,37,40 Patonay and colleagues reported a highly stereoselective reaction that provided a high yield of a rearranged arylsulfonate as a diastereomerically pure alcohol, 159 (Scheme 42). 37 The authors chose not to propose a hypothesis to explain the high degree of observed stereoselectivity; however, it seems likely that the existing chiral center on the dihydropyrone ring exerts an influence on the stereochemistry of the sterically crowded 4-membered ring spirocyclic Meisenheimer adduct, 158, formed in the course of the reaction.…”

“…However, the reaction has recently begun to receive a more systematic investigation by researchers such as Takashi Hirota [18][19][20][21][22][23][24][25][26][27][28] and Timothy Snape. [29][30][31] Despite our awareness of the Truce-Smiles rearrangement for 60 years, there remain many unanswered questions about the scope and limitations of this reaction. In this review, we seek to summarize the current state of our understanding of the reaction and hope to inspire continued progress.…”