A Highly Efficient Friedel–Crafts Reaction of Tertiary α‐Hydroxyesters or α‐Hydroxyketones to α‐Quaternary Esters or Ketones

Abstract

A catalytic Friedel-Crafts arylation of α-hydroxyesters or α-hydroxyketones with electron-rich aromatic compounds to furnish α-quaternary esters/ketones has been developed. The cheap and easy to handle catalyst HClO(4) (70 %, aq) was identified as a powerful catalyst for this arylation reaction.

Metal Free, Direct and Selective Deoxygenation of α‐Hydroxy Carbonyl Compounds: Access to α,α‐Diaryl Carbonyl Compounds

“…HClO 4 to give 2‐(4‐methoxyphenyl)‐1,2,2‐triphenylethanone ( 6 , Scheme ). This reaction is similar to the Friedel‐Crafts arylation reaction of alcohols occurring through carbocation under acidic conditions . Isolation of 3 as rearangement product during deoxygenation of α‐hydroxy ketone 1k also suggests the intermediacy of α‐carbonyl carbenium ion (see supporting information).…”

Recent Advances in Direct Catalytic Dehydrative Substitution of Alcohols

“…51 In this context, Wang and Zhou reported the perchloric acid catalyzed thiolation of 3-hydroxyoxindoles, 52 whilst in a comprehensive series of reports, Bisai and co-workers explored the Lewis acid catalyzed Friedel-Crafts reaction of the same substrates. 53 The Zhou group also demonstrated the use of catalytic perchloric acid in the arylation of α-keto benzylic alcohols, 54 whilst Singh and co-workers reported an InBr 3catalyzed azidation of α-keto benzylic alcohols. 55 In 2015, Hall, McCubbin and co-workers disclosed a boronic acid catalyzed Friedel-Crafts reaction employing benzylic alcohols.…”

A Brønsted Acid Catalyzed Cascade Reaction for the Conversion of Indoles to α‐(3‐Indolyl) Ketones by Using 2‐Benzyloxy Aldehydes

“…For example, classical transition‐metal‐catalyzed cross‐coupling reactions suffer from the requirement of an expensive catalyst as well as ligand, prefunctionalized halides or pseudo halides, and the use of excessive strong bases, which suppresses the economic viability . Similarly, traditional Friedel–Crafts arylation reactions mainly rely on elaborated tertiary alcohols with electron‐donating aryl substituents, harsh conditions, and strong acids with high catalyst loading . An elegant Cu II ‐mediated base‐promoted enolate coupling of indole with ketone was reported by Baran et al.…”