To a solution of [2-(4-[1,3]dioxolan-2-yl-phenyl)-3-phenyl-[1,6]naphthyridin-5-yl]-hydrazine (3-4, 1.6 g, 4.2 mmol) and toluenesulfonic acid monohydrate (79 mg, 0.4 mmol) in 3:1 toluene:MeOH (16 mL) was added trimethyl orthoformate (0.58 mL, 12.5 mmol). The mixture was heated to 100° C. in a microwave reactor for 1 hr. The reaction mixture was then concentrated in vacuo. The solid was collected and dried with toluene azeotropically to give the title compound which was used for next step without further purification. LRMS m/z (M+1) Calcd: 395.1. Found 395.2.
