Cross-Dehydrogenative-Coupling of Alkoxybenzenes with Toluenes: Copper(II) Halide Mediated Tandem Halo/Benzylation of Arenes

Temperature-Assisted Generation of Arylmethyl Radicals from Bis(arylmethyl)tin Dichlorides: Efficient Reagents for C s p 3 ${{{\bf C}}_{{{\bf s p}}^{3}}}$ - C s p 2 ${{{\bf C}}_{{{\bf s p}}^{2}}}$ Bond-Forming Reactions

The oxidative-addition reaction between an arylmethyl chloride (RCH₂ Cl; R=1-C₁₀ H₇ , 2,4,6-Me₃ C₆ H₂ , 4-MeC₆ H₄ , 3-MeC₆ H₄ , C₆ H₅ , 4-ClC₆ H₄ ) and tin powder in boiling toluene produces bis(arylmethyl)tin dichlorides, [(RCH₂ )₂ SnCl₂ ] in good yields. At 160 °C in mesitylene bis(1-naphthylmethyl)tin dichloride undergoes Sn-C homolytic cleavage to generate two 1-naphthylmethyl radicals (1-C₁₀ H₇ CH₂ ⋅) which were trapped by TEMPO (C₉ H₈ NO⋅). Subsequently, the radicals (RCH₂ ⋅) produced in this manner were utilized for efficient substitution reactions with electron-rich arenes (R'H; R'=2,4,6-Me₃ C₆ H₂ , 1,2,4,5-Me₄ C₆ H, 1,2,3,4,5-Me₅ C₆ ) to obtain a variety of unsymmetrical diarylmethanes (RR'CH₂ ). The addition of one equivalent of iodine (I₂ ) to the reaction mixture resulted in a significant increase in the yields of coupled products.

Cross-dehydrogenative coupling involving benzylic and allylic C–H bonds

Benzylic and allylic C–H bonds are coupled with C(sp)–H, C(sp²)–H and C(sp³)–H bonds in a straightforward and high atom-economic manner.

Transition metal-free cross-dehydrogenative arylation of unactivated benzylic C–H bonds

The cross-dehydrogenative arylation of benzylic C–H bonds with arenes provides straightforward access to synthetically useful 1,1-diarylmethanes, from readily available starting materials.

Benzylarylation of N-Allyl Anilines: Synthesis of Benzylated Indolines

An unprecedented benzylic C-H functionalization of methyl arenes across unactivated alkenes is presented. In the presence of MnCl₂·4H₂O and di- tert-butyl peroxide, N-allyl anilines underwent benzylation/cyclization cascade to give benzylated indolines, which are a previously unmet synthetic goal. This protocol features simple operation, broad substrate scope, and great exo selectivity.

Green, Mild, and Efficient Friedel-Crafts Benzylation of Scarcely Reactive Arenes and Heteroarenes under On-Water Conditions

Metal-free Friedel-Crafts benzylation (FCB) of scarcely reactive arenes and heteroarenes was performed under on-water conditions by an environmentally sustainable procedure. The catalytic strategy exploits the hydrophobicity of the resorcinarene macrocycle 1 a. The proposed mechanism is based on the activation of benzyl chloride by H-bonding interactions with catalyst 1 a. In fact, under on-water conditions the hydrophobic amplification of the strength of the H-bonding interactions between the OH groups of the resorcinarene catalyst and the chlorine atom of benzyl chloride leads to polarization of the C-Cl bond, which consequently promotes electrophilic attack of the π nucleophile. Thus, many arenes and heteroarenes were efficiently benzylated under mild on-water conditions by using resorcinarene 1 a as catalyst. The FCB of benzene is industrially relevant for the synthesis of diphenylmethane, and hence the on-water procedure was extended to the gram-scale synthesis of diphenylmethane, starting from benzene and benzyl chloride in the presence of resorcinarene catalyst 1 a.