Intramolecular Diels–Alder and [3+2] Cycloaddition Reactions in the One-Pot Synthesis of Epoxypyrrolo[3,4-g]indazoles

Diels–Alder and [3+2] cycloaddition reactions are two dynamic tools for synthesis of diverse organic compounds. Recently employment of IMDA reaction in acetylene based isocyanide multicomponent reactions has found remarkable interests.1 Additionally, in continuation of our previous works in acetylene-based isocyanide multicomponent reaction,2 we were interested in the reaction of isocyanides 1, dialkyl acetylene dicarboxylates 2 and 2-furan carboxylic acid 3, which led to 1,3-dioxoepoxyisoindoles 4. In the next step, we decided to investigate the reactivity of the double bond in the structure of 1, 3-dioxoepoxyisoindole 4 toward [3+2] cycloaddition reaction. To achieve this goal, hydrazonoyl chloride 5 with an equivalent amount of triethylamine were added to the reaction mixture and the reaction outcome was the epoxypyrrolo[3,4-g]indazoles 6/6ʹ in the form of two diastereomers, products were verified by mass, IR, 1H NMR, 13C NMR spectra and X-ray crystallography.

Keywords:

Isocyanides , Dialkyl acetylene dicarboxylates , 2-Furancarboxylic acid , Epoxypyrrolo[3 , 4-g]indazoles , IMDA , [3+2] Cycloaddition , Oxabicyclo Compounds