Divalent tin compound, Sn2TiO4, was synthesized by a simple solid-state reaction of component oxides under 2.45 GHz microwave irradiation. The reaction rapidly proceeds with the diffusion of hot Sn2+ species toward TiO2 to form Sn2TiO4 within 1 min. A drastic enhancement of reaction kinetics could be achieved under thermally nonequilibrium conditions induced by strong coupling of SnO with microwave energy. This makes it possible to avoid the disproportionation reaction of SnO to Sn and SnO2, giving us a new synthetic strategy for direct synthesis of Sn2+ compounds.