Protecting group-free use of alcohols as carbon electrophiles in atom efficient aluminium triflate-catalysed dehydrative nucleophilic displacement reactions

Abstract

Benzylic and allylic alcohols are rendered electrophilic without chemical modification by the use of aluminium triflate as catalyst. The reaction succeeds with alcohol, thiol, carbon and nitrogen nucleophiles. When phenols are employed as nucleophiles, C-alkylation ensues. An advanced application of the method is demonstrated in the synthesis of 2H-chromenes and their N and S analogues.Scheme 4 Synthesis of 2H-chromenes in Al(OTf) 3 -catalysed cyclisation reactions. Scheme 5 Synthesis of 2H-chromene from an isomeric substrate. Scheme 3 Reactions of activated alcohols with p-toluenesulphonyl amide. Scheme 6 Synthesis of dihydroquinoline in an Al(OTf) 3 -catalysed dehydrative cyclisation. 42170 | RSC Adv., 2017, 7, 42168-42171This journal is

Scope and advances in the catalytic propargylic substitution reaction

“…Use of Al(OTf) 3 in the direct nucleophilic displacement of OH in 'activated' systems with several nucleophiles were reported by Williams and co-workers in 2017. 54 This efficient process allows the ready synthesis of a wide range of benzylic and allylic substituted products in very high yields with water as the only by-product.…”

Scope and Mechanism of the Ruthenium-Catalyzed Dehydrative C–H Coupling of Phenols with α,β-Unsaturated Carbonyl Compounds: Expedient Synthesis of Chromene and Benzoxacyclic Derivatives

“…The proposed mechanistic pathway suggests that the phenolic intermediate 5 could be independently generated from the reaction of a phenol-substituted allylic alcohol with the ruthenium catalyst 1 . To establish its participation for the coupling reaction, we prepared the substrate ( E )-2-(1-hydroxy-3-phenylallyl)­phenol ( 7 ) by following a literature procedure . The treatment of 7 with the ruthenium catalyst 1 under the standard reaction conditions smoothly led to the chromene product 2aa in 76% isolated yield (eq ).…”

“…To establish its participation for the coupling reaction, we prepared the substrate (E)-2-(1-hydroxy-3-phenylallyl)phenol ( 7) by following a literature procedure. 21 The treatment of 7 with the ruthenium catalyst 1 under the standard reaction conditions smoothly led to the chromene product 2aa in 76% isolated yield (eq 7). The result indicates that the cationic Ru−phenoxy complex 5, which would be formed from the deprotonation of phenolic proton and the coordination of the olefinic group of the substrate 7, is the key species for the formation of the chromene product 2.…”

Novel hybrids derived from aspirin and chalcones potently suppress colorectal cancer in vitro and in vivo

“…Synthesis of intermediates 5a-f. Intermediates 5a-f were prepared according to a method described previously [82][83][84][85] with minor modification. Triphenyl phosphine (PPh 3 , 1 mmol) was dissolved in anhydrous THF (2 mL).…”

“…Synthesis of 6a-p. Chalcones 6a-p were prepared using a known synthetic method procedure. 85 A mixture of a corresponding aldehyde (1.0 mmol) with intermediates 5a-f (1.0 mmol) in anhydrous toluene (2.0 mL) was stirred at 60°C under nitrogen for 8 h. The solvent was evaporated in vacuo to give the corresponding crude intermediates 6a-p, which were directly used in the next step without further purification (data in the ESI †).…”