Temperature-Assisted Generation of Arylmethyl Radicals from Bis(arylmethyl)tin Dichlorides: Efficient Reagents for - Bond-Forming Reactions.

Abstract

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.