In situ generation and reactions of p-(trifluoromethyl)benzyl electrophiles: an efficient access to p-(trifluoromethyl)benzyl compounds

Access to Substituted 1,1-Diarylalkanes by Friedel-Crafts Benzylations Mediated by FeCl3-based Deep Eutectic Solvents

The development of new, more efficient Friedel-Crafts benzylation methodologies that provide access to 1,1-diarylalkanes is an important objective of interest for the production of pharmaceuticals and fine chemical products. In this regard, this study introduces a novel synthetic route to 1,1-diarylalkanes conducted in the Deep Eutectic Solvent (DES) 3 FeCl3 ⋅ 6 H2O/Gly, which serves as both a reaction medium and promoter. Under these conditions, Friedel-Crafts benzylations of various arenes bearing activating and deactivating ortho-/para-directing groups, can be performed using diverse benzylating reagents such as styrenes, alcohols, acetates, ethers, and chlorides. Importantly, highly electronically deactivated electrophiles, including those with CF3 and NO2 groups, are suitable substrates. This methodology provides a wide range of asymmetric 1,1-diarylalkanes (up to 132 examples) with generally good yields and high regioselectivities. The efficiency of this approach was demonstrated with the multigram-scale synthesis (10 mmol) of 1-phenyl-1-xylyl ethane (PXE), a liquid with great industrial applicability. Moreover, the Fe(III)-based DES could be reused for 20 consecutive cycles with no appreciable erosion of the yields.

Tandem Cyclization of o-Hydroxyphenyl Propargyl Alcohols with Thionucleophiles: A Metal-Free and Modular Access to 3-Fluoroalkylsulfonyl/Thio Benzofurans

Despite both fluoroalkylsulfonyl groups and benzofurans are important bioactive moieties, the construction of fluoroalkanesulfonylated benzofurans that incorporate these two fragments remains underdeveloped. Here, we report a tandem cyclization protocol to construct a wide range of 3-fluoroalkylsulfonyl benzofurans using readily accessible o-hydroxyphenyl propargyl alcohols and sodium fluoroalkanesulfinates. Furthermore, this synthetic strategy can also be adapted to prepare 3-thio benzofurans by changing the S-nucleophiles to thiols or thiophenols.

Trifluoromethylations of (Hetero)arenes and Polarized Alkenes Using Trifluoroacetic Anhydride under Photoredox Catalysis

A novel trifluoromethylation of (hetero)arenes and polarized alkenes using simple trifluoroacetic anhydride (TFAA) as the low price CF₃ source under photoredox catalysis was developed without using additives such as bases, hyperstoichiometric oxidant, or auxiliaries. The reaction showed excellent tolerance, including to some important natural products and prodrugs, even on the gram scale and extended to ketones. This simple protocol provides a practical utilization of TFAA. Several perfluoroalkylations and trifluoromethylation/cyclizations were successfully achieved under identical conditions.

Csp3-H bond functionalization of amines via tunable iminium ions: divergent synthesis of trifluoromethylated arylamines

A series of tunable iminium ions, generated in situ by the condensation of 4-trifluoromethyl-p-quinols with cyclic amines, can lead to the divergent synthesis of trifluoromethylated arylamines in a single step via redox-neutral isomerization. The direct α- and β-functionalization of saturated amines can be achieved regioselectively under mild conditions.