This study reports a mild and efficient synthetic protocol for the synthesis of symmetrical and unsymmetrical diarylmethanes (DAMs). Using DMSO as the C1 source and TMSOTf as the Lewis acid promoter, a series of functionalized symmetrical and unsymmetrical DAMs were synthesized in high yields. Gratifyingly, DMSO plays a dual role as a solvent and a C1 source and can also be replaced with its deuterated counterpart, DMSO-d6, enabling the incorporation of the -CD2 moiety into the diarylmethane skeleton. The developed approach has been applied to a wide range of substrates having various functional groups, and this protocol has also been extended to the synthesis of an anti-breast cancer agent and an anticoagulant agent using common feedstock compounds. In addition, the postulated mechanism has been explicitly demonstrated via control experiments.