Lewis Acid Catalyst Free Electrophilic Alkylation of Silicon‐Capped π Donors in 1,1,1,3,3,3‐Hexafluoro‐2‐propanol

Abstract

A credit to donation: A diverse range of electrophilic addition reactions, conventionally carried out using Lewis acid catalysts, have been performed in electrophilic media without acidic reagents. 1,1,1,3,3,3‐Hexafluoro‐2‐propanol (HFIP) acts as an efficient hydrogen‐bond donor and highly polar solvent for a wide range of substrates in reactions with Si‐capped π donors.

A facile and efficient synthesis of 2-amino-3-cyano-4H-chromenes and tetrahydrobenzo[b]pyrans using 2,2,2-trifluoroethanol as a metal-free and reusable medium

“…Therefore, the search continues for a better catalyst for the synthesis of pyrans in terms of operational simplicity, reusability, economic viability, and greater selectivity. The use of fluorinated solvent, as chemical reaction media in place of conventional volatile organic solvents, has grown dramatically in recent years [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Fluorinated alcohols possess interesting physiochemical properties, which include lower boiling points and higher melting points than their non-fluorinated counterparts, high polarity, strong hydrogen bond donation properties and the ability to solvate water.…”

Overcoming Product Inhibition in Catalysis of the Intramolecular Schmidt Reaction

“…Compared to their non-fluorinated alcohol analogues, TFE and HFIP have low nucleophilicity, low pKa, high ionizing power, high polarity, ability to solvate anions, and are strong hydrogen bond donors. 15 Accordingly, they are often used as solvent, co-solvent, or a Lewis acid substitute 15e,16 in oxidations, 17 or in ring opening reactions of oxiranes, cycloaddition, and deprotection reactions. 15b,l5d,l5f Their utility has been attributed to the strong hydrogen bond donor ability of these solvents.…”

The Future of Catalysis by Chiral Lewis Acids

“…In one recent report [155], highly substituted dihydropyrones were produced with high enantiocontrol and moderate diastereoselectivity in sequential aldol and oxy-Michael reactions of ynones and aldehydes using a chiral copper (I) catalyst for the aldol reaction and a subsequent AgOTf catalyst for the Michael reaction (Scheme 34). The use of perfluorinated alcohols accelerates the aldol reaction, and their addition to accelerate reactions is becoming increasingly common [156].…”