Abstract
A review on the tandem [4+2]/[3+2] cycloaddition reactions of 1,3,4-oxadiazoles with alkenes is presented. This reaction presents a powerful synthetic tool in the construction of complex polycyclic molecules in a one-pot reaction. Special attention is paid to synthesis of [n]polynorbornane and oxanorbornyl systems. In continuation, a review on the 1,3,4-oxadiazole reactions used in stereoselective total synthesis of alkaloids is given. Both intermolecular and intramolecular tandem [4+2]/[3+2] reactions are discussed. Stereospecificities and mechanistic rationale of various reactions are supported by quantum-chemical calculations (RHF/6-31G*).
Keywords: Diels-Alder reaction, dipolar cycloaddition, oxadiazoles, polycyclic molecules, reaction mechanism, Tandem cycloaddition reactions, norbornane, Diels-Alder, 7-oxanorbornane subframe, COCOC-[5]polynorbornane, COC-[3]polynorbornane, 2,5-bis-trifluoromethyl-1,3,4-thiadiazoles, norbornene-2,3-maleimide, X-ray crystallography, phthalimido, radial chromatography, bis-quinoxaline, 7-oxanorbornenes, Alder-Rickert reaction, 2,9-dimethylisobenzofuran, 7-tert-butoxynorbornadiene, aromatization, B3LYP, BMK, MP2, TS172, TS173