Microwave-Assisted Transition-Metal-Catalyzed Synthesis of N-Shifted and Ring-Expanded Buflavine Analogues

摘要

Two novel and efficient strategies for the synthesis of hitherto unknown N-shifted and ring-expanded buflavine analogues are presented.Construction of the medium-sized ring system of the title molecules,a difficult task due to the high activation energy needed for the ring-closure with the additional rigidity imposed by the biaryl skeleton,was achieved by using Suzuki-Miyaura biaryl coupling and a ring-closing metathesis reaction as the key steps.The combination of a second-generation Grubbs catalyst and microwave irradiation proved to be highly useful in generating the otherwise difficult to obtain medium-sized ring system of the buflavine analogues.