A novel synthesis method for the construction of 3-coumaranones from the reaction of two molecules, calcium carbide and salicylaldehyde, was reported. Various 2-methyl-2-vinylbenzofuran-3(2H)-ones could be obtained in moderate yields in the absence of a metal catalyst. The salient features of this protocol involve widely available starting materials, an inexpensive and easy-to-handle alkyne source, and a cost-efficient route. The reaction mechanism was verified by density functional theory calculations of possible intermediates and corresponding transition states.