Highly Efficient and Mild Cascade Reactions Triggered by Bis(triphenyl)oxodiphosphonium Trifluoromethanesulfonate and a Concise Total Synthesis of Camptothecin

A mild and efficient cascade methodology is reported to construct variously substituted indolizino[1,2-b]quinolin-9(11H)-ones. Efficiently triggered by bis(triphenyl)oxodiphosphonium trifluoromethanesulfonate under mild conditions, this cascade achieved significant enhancements in chemical yields. Utilizing this highly efficient domino reaction followed by a Sharpless dihydroxylation, an eight-step total synthesis of camptothecin was accomplished from a known pyridine derivative in direct fashion with an overall yield of 47% and 95% ee.