Baeyer–Villiger Oxidations with Hydrogen Peroxide in Fluorinated Alcohols: Lactone Formation by a Nonclassical Mechanism

Abstract

What a difference the solvent makes! Unlike in conventional solvents, nonstrained ketones such as cyclohexanone react smoothly with hydrogen peroxide in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) to give lactones. The reaction proceeds via an isolatable spiro‐bisperoxide, which undergoes a highly exothermic acid‐catalyzed rearrangement to two equivalents of lactone (see Equation and IR thermogram).

A facile and efficient synthesis of β-amino alcohols using 2,2,2-trifluoroethanol as a metal-free and reusable medium

“…Fluorinated alcohols are well-known as a polar solvent [34,35] of high ionizing power [36], low nucleophilicity [37][38][39][40][41] and have been the subject of considerable interest since their introduction as ''green'' solvents for reactions. Besides their usefulness as powerful reaction media, fluorinated alcohols have been well recognized as efficient catalysts and successfully applied in many organic reactions [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60]. The most commonly used and cheapest fluorinated alcohols are trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP), which are available on a commercial scale.…”

Baeyer‐Villiger oxidation tuned to chemoselective conversion of non‐activated [18F]fluorobenzaldehydes to [18F]fluorophenols

“…This presumably is facilitated by a further protonation of the Criegee intermediate by H 2 SO 4 as well as by a stabilisation of the protonated form by TFE. It is known from literature that fluorinated solvents have a crucial influence on the mechanism of the BVO and thus on the formation of the product . In general, because of their strong negative inductive effect, polyfluorinated solvents like TFE are characterised by an increased acidity of the hydroxyl group, a high ionising power, and a lower nucleophilicity .…”

One-step, synthesis of Hantzsch esters and polyhydroquinoline derivatives in fluoro alcohols

“…The most commonly used and cheapest fluorinated alcohols are 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), which are available on a commercial scale and with a relatively low toxicity [29][30]. These alcohols display interesting properties, such as solvent, co-solvent, or additives in various catalytic processes and consequently they are often used in studies of peptide and protein structure [31], solvolysis [32][33][34][35], their effect on various organic transformations [36][37][38][39][40][41] and notably the activation of hydrogen peroxide for oxidation, epoxidation and the Baeyer-Villiger rearrangement [42][43][44][45][46][47][48]. In continuation of our effort towards the development of efficient synthetic procedures for multicomponent reactions, we turned our attention towards the synthesis of 1,4-dihydropyridines and polyhydroquinoline derivatives.…”