Exploiting hexafluoroisopropanol (HFIP) in Lewis and Brønsted acid-catalyzed reactions

Abstract

Hexafluoroisopropanol (HFIP) is a solvent with unique properties that has recently gained attention for promoting a wide range of challenging chemical reactions. It was initially believed that HFIP was almost...

Promoting the Furan Ring‐Opening Reaction to Access New Donor–Acceptor Stenhouse Adducts with Hexafluoroisopropanol

“…[23,27] Unfortunately,a ll our attempts to use metal-based Lewis acids in DASA synthesis resulted in degradation of the product or starting materials. Inspired by the work of Gandon and co-workers and their successful application of HFIP in the aza-Pinacatelli rearrangement, [26,31] we next explored the use of HFIP as am ild Lewis/Brønsted acid in DASA synthesis.H FIP has ah igh polarity and ionization potential as well as moderate acidity (pK a = 9.3) in combination with low nucleophilicity and astrong hydrogen bond donating ability,which could possibly provide away of assisting in the electrophilic activation of the furan adduct and stabilizing charged intermediates. [30,31] Furthermore,a sac onsequence of its low boiling point (b.p.…”

“…[26] HFIP has recently gained much attention for efficiently promoting aw ide range of organic reactions catalyzed by Lewis and Brønsted acids. [30,31] Herein, we report the use of HFIP as am ild Lewis/ Brønsted acid in the synthesis DASA to promote the ringopening reaction of furan adducts for facile access to abroad range of DASA photoswitches,i ncluding ar ange of new DASA derivatives bearing deactivated amine donors that were previously unreactive.Furthermore,weshow that HFIP shifts the DASA equilibrium to the open form through hydrogen-bonding interactions,t hereby simplifying work-up and purification procedures and increasing the overall yields of the isolated products.T his method is also applied to prepare DASA-polymer conjugates,w ith the required time for functionalization reduced from days to several hours and allowing the preparation of more structurally diverse DASA materials.…”

1,2‐Benzothiazine Derivatives from Sulfonimidamides by Metal‐Catalyzed Annulation Reactions in Solution and under Solvent‐Free Mechanochemical Conditions

“…Using hexafluoro-2-propanol (HFIP) instead of TFE as solvent, improved the yield of 11 aa to 52% ( Table 2, entry 10). [19] A subsequent screening of other solvents confirmed the pronounced influence of the reaction media. To our great surprise, we had to note that in none of the tested systems (1,2-DCE, DCM, MeOH, EtOH, MeCN, and toluene), product 11 aa was formed ( Table 2, entries [11][12][13][14][15][16].…”

“…as additive in TFE to the reaction of sulfonimidamide 1 a and diazoketone 10 a provided product 11 aa in 34% yield (Table 2, entry 8). Using hexafluoro‐2‐propanol (HFIP) instead of TFE as solvent, improved the yield of 11 aa to 52% (Table 2, entry 10) [19] . A subsequent screening of other solvents confirmed the pronounced influence of the reaction media.…”

Trifluoroethanol‐mediated Decarboxylative Addition Reactions of β‐Ketoacids with Diverse Electrophiles

“…Over the past two decades, the fluorinated alcohols have been recognized as magic solvents in a variety of reactions owing to their unique properties such as low nucleophilicity, strong hydrogen-bond donating ability, mild acidity and high ionization power. [4] A great deal of efforts have been devoted to the utilization of fluorinated alcohols in metal-and organo-catalyzed synthetic methodologies. Intriguingly, more and more synthetic methodologies which are only performed in fluorinated alcohols without any additives or catalysts have been discovered recently.…”