Recent Advances in the Smiles Rearrangement: New Opportunities for Arylation

Abstract

The Smiles rearrangement has undergone a renaissance in recent years providing new avenues for non-canonical arylation techniques in both the radical and polar regimes. This Short Review will discuss recent applications of the reaction (from 2017 onwards), including its relevance to areas such as heterocycle synthesis, functionalisation of alkenes and alkynes as well as glimpses at new directions for the field.

Revisiting the formation mechanism of diarylamines via Smiles rearrangement

“…[3] However, the electronic and, above all, steric properties of the substituents limit the latter method. [4,5] An alternative route to synthesize sterically hindered compounds is the Smiles rearrangement. [5,6] Encouraged by recent works on the Smiles rearrangement of sulfinamide, [5,7,8] Greaney and co-workers explored the reactivity of 4-nitro-N-phenylbenzenesulfinamide (1) as a precursor of 4-nitrodiphenylamine (3, Scheme 1).…”

“…[4,5] An alternative route to synthesize sterically hindered compounds is the Smiles rearrangement. [5,6] Encouraged by recent works on the Smiles rearrangement of sulfinamide, [5,7,8] Greaney and co-workers explored the reactivity of 4-nitro-N-phenylbenzenesulfinamide (1) as a precursor of 4-nitrodiphenylamine (3, Scheme 1). [1] After obtaining good yields of 3 in N,N-dimethylformamide (DMF) as solvent, the authors examined the substrate scope of the N-aryl group, achieving similar success in the corresponding products.…”

Synthesis of 7-Aminocoumarins from 7-Hydroxycoumarins via Amide Smiles Rearrangement

“…The Smiles rearrangement presents a classical and underutilized route for incorporating nitrogen functionality into aromatic systems. 12 − 14 Bayles and co-workers first detailed the rearrangement of 2-aryloxypropanamides into corresponding anilide products when treated with sodium hydride and heated in DMF or hexamethylphosphoramide. 15 , 16 Subsequent investigations have expanded this amide-based reactivity for the conversion of phenols into primary or secondary anilides or anilines upon hydrolysis but remain limited by harsh conditions and high temperatures.…”

“…The Smiles rearrangement presents a classical and underutilized route for incorporating nitrogen functionality into aromatic systems. − Bayles and co-workers first detailed the rearrangement of 2-aryloxypropanamides into corresponding anilide products when treated with sodium hydride and heated in DMF or hexa­methyl­phosphoramide. , Subsequent investigations have expanded this amide-based reactivity for the conversion of phenols into primary or secondary anilides or anilines upon hydrolysis but remain limited by harsh conditions and high temperatures. − Owing to its electron-withdrawing lactone, we postulated that coumarins may prove amenable to a milder process that might avoid the competitive reactivity of conjugate addition at the 4-position or lactone opening. ,, We were encouraged by a recent report of a tandem substitution–Smiles rearrangement of aminophenols on 4-bromocoumarins at relatively low temperatures . We therefore sought to determine whether 7-hydroxycoumarins may be efficiently converted to a diverse array of 7-aminocoumarins via an amide-based rearrangement–hydrolysis strategy.…”

Visible-Light-Photocatalyzed Dicarbofunctionalization of Conjugated Alkenes with Ketone-Based Dihydroquinazolinones

“…In this arena, the Nevado group revealed the potential of N -aryl- N -(arylsulfonyl)­acrylamides toward catalytic 1,2-aryltrifluoromethylation with Togni reagent via radical Truce–Smiles rearrangement . Such transformation involves tandem trifluoromethylation/aryl migration/desulfonylation events in a unified single operation, which encases the advent of an aryl transfer, as well as desulfonylation tactics . Since then, radical dicarbofunctionalization of N -aryl- N -(arylsulfonyl)­acrylamides, including arylalkylation and diarylation, has been substantially spurred to enable the rapid construction of sterically congested all-carbon quaternary α-stereocenters, which is, indeed, a formidable task .…”