Synthesis Of H-pyrazolo[5,1-a] Isoqumolines Via Tandem Reactions

Diversity-oriented synthesis has been used as a powerful method for thegeneration of molecular complexity and diversity. Among the strategies utilized,tandem reaction has been recognized as an efficient route for the construction ofscaffolds of natural products.This dissertation is mainly focused on the methodology development for thesynthesis of H-pyrazolo[5,1-a]isoquinolines via tandem reactions.(1) A silver triflate-catalyzed reaction of N’-(2-alkynylbenzylidene)hydrazidewith allenoate using DCE and DMF as a mixed solvent is described, which providesan efficient approach for the access to diverse H-pyrazolo[5,1-a]isoquinolines. Thereaction proceeded through6-endo-cyclization,[3+2] cycloaddition, andaromatization.(2) A cascade reaction of N’-(2-alkynylbenzylidene)hydrazide with allenoate inthe presence of dioxygen co-catalyzed by silver triflate and copper(Ⅱ)acetate undermild conditions is developed, leading to2-carbonyl H-pyrazolo[5,1-a]isoquinolines. Itwas found that the carbonyl oxygen in the products was from dioxygen and thereaction proceeded through a peroxy-copper(III) intermediate.