Microwave-Accelerated Alkylation of Arenes/Heteroarenes with Benzylic Alcohols Using Antimony(III) Chloride as Catalyst: Synthesis of O-Heterocycles

Abstract

An efficient protocol for alkylation of electron-rich arenes/heteroarenes with benzylic alcohols under microwave irradiation using antimony(III) chloride as catalyst has been developed. The mild reaction conditions, high yields, operational simplicity, and applicability to various substrates render the approach a useful route for the synthesis of diaryl/triarylalkane. In addition, a new route for the conversion of ortho-alkenylated phenols into functionalized O-heterocycles has been accomplished.

Friedel-Crafts Benzylations Mediated by FeCl3-based Deep Eutectic Solvents. Access to Substituted 1,1-diarylalkanes using Activated and Deactivated Electrophiles

“…Despite its historical significance, this reaction faces significant challenges relates with the poor reactivity of deactivated aromatic substrates (both nuclophiles and electrophiles), the employment of both stoichiometric amount of activators and hazardous reagents (many alkyl halides are toxic lachrymators and generate irritating hydrogen halide byproducts), the needed of harsh reaction conditions and the low selectivity. To overcome these limitations and, additionally, meet the currently required criteria for atomic economy and sustainable chemistry, a handful of methodologies have recently emerged that use catalytic amount of activators and readily acces-sible electrophilic species such as styrenes [62][63][64][65][66][67] alcohols, [68][69][70][71][72][73][74][75][76][77][78][79][80][81] ethers, [69,82,83] or acetates [69,70,84] among others. [85][86][87][88] Thus, and after the publication in 1997 of the work by Fukuzawa et al describing the benzylation of activated arenes with benzyl alcohols catalyzed by scandium triflate, [71] the use of metallic-based catalysts in the direct Friedel-Crafts benzylation reaction has been extended to a wide variety of transition metals such as Au, [70] Co, [63,84] Fe, [64,69,83,85,86,…”

“…To overcome these limitations and, additionally, meet the currently required criteria for atomic economy and sustainable chemistry, a handful of methodologies have recently emerged that use catalytic amount of activators and readily acces-sible electrophilic species such as styrenes [62][63][64][65][66][67] alcohols, [68][69][70][71][72][73][74][75][76][77][78][79][80][81] ethers, [69,82,83] or acetates [69,70,84] among others. [85][86][87][88] Thus, and after the publication in 1997 of the work by Fukuzawa et al describing the benzylation of activated arenes with benzyl alcohols catalyzed by scandium triflate, [71] the use of metallic-based catalysts in the direct Friedel-Crafts benzylation reaction has been extended to a wide variety of transition metals such as Au, [70] Co, [63,84] Fe, [64,69,83,85,86,89] Ir, [76,82,84,90,91] Pt,…”

NHC as a Ligand in Heterobimetallic Catalysis: An Insight into a Catalytic Friedel–Crafts-like Reaction

“…Over the past two decades, the construction of a C–C bond by the direct reaction of a C–H bond with a C–OH bond, without prefunctionalization, has been viewed as an excellent addition to the realm of sustainable chemistry. − The reaction has the potential to be showcased as one of the beautiful examples in green chemistry by virtue of the fact that water is the only byproduct. − In 2005, we disclosed the first example of heterobimetallic catalysis using a transition metal–tin motif toward coupling an arene and alcohol . We termed this reaction catalytic Friedel–Crafts-like alkylation (FCA), as initial studies pointed out that it may not be a case of true C–H activation but rather C–H functionalization.…”