Enolization rates control mono- versus di-fluorination of 1,3-dicarbonyl derivatives

Abstract

All rate constants for fluorination and enolization are determined.

Kinetics of Electrophilic Fluorination of Steroids and Epimerisation of Fluorosteroids

“…Thus, taking these factorst ogether,w ep erformed kinetics studies using water and MeOH as co-solvents for fluorination of 17. [22] and enol ester 17 along their fluorination reaction coordinates. Product analyses of crude reaction mixturesb yL C-MS were also unchanged by the addition of MeOH or water,a nd thus we concludet hat the use of these co-solvents offers no advantage to the fluorination process.…”

Bench‐Stable Electrophilic Fluorinating Reagents for Highly Selective Mono‐ and Difluorination of Silyl Enol Ethers

“…(1)). For the difluorination of 1,3‐dicarbonyl compounds with NFSI, the second fluorination step is known to be faster than the first one [29] . Notably, 5 a was not protonated upon treatment with 1 a , and 5 a was completely recovered (Scheme 3, Eq.…”

Reactivities of electrophilic N–F fluorinating reagents

“…To understand the factors that determine selectivity between mono-and di-fluorination, we performed kinetics studies on keto-enol tautomerism and fluorination processes. 122 We utilized a photo-switching method for the determination of enolization rates in 1,3-diaryl-1,3-dicarbonyl derivatives 134 and their 2-fluoro analogues 135.…”

“…Secondly, we extended our kinetics studies to determine the rates of fluorination of enolic 2-fluoro-1,3dicarbonyls 135a,c-e using UV-vis spectrophotometry (Scheme 12a, Table 15). 122 Activation parameters determined for fluorinations of 135a and 135d using Selectfluor™ 25 are included in Table 14. We determined that the addition of a second fluorine atom occurs at a similar or greater rate than that of the addition of the first fluorine atom, which is represented by the krel' values according to Equation 8.…”