Recent Applications of Ammonium Ylide Based [2,3]-Sigmatropic and [1,2]-Stevens Rearrangements To Transform Amines into Natural Products

Abstract Ammonium ylide based [2,3]-sigmatropic and [1,2]-Stevens rearrangements enable the transformation of tertiary amines into rearranged and functionalized intermediates en route to many polycyclic natural product targets. Herein, we summarize recent applications of these rearrangement reactions in formal and total synthesis endeavors while highlighting innovative improvements to these transforms. 1 Introduction 2 Ammonium Ylide Based [2,3]-Sigmatropic Rearrangements in Natural Product Synthesis 2.1 (–)-Cephalotaxine 2.2 (±)-Amathaspiramide F 2.3 (–)-Cephalezomine G and Its C3 Epimer 2.4 (±)-Strictamine 2.5 (–)-Doxycycline 3 [1,2]-Stevens Rearrangements Toward Natural Products 3.1 Ring-Expanding [1,2]-Stevens Rearrangements en route to (±)-Tylophorine, (±)-7-Methoxycryptopleurine, and (±)-Xylopinine 3.2 Enantioselective Synthesis of Iboga Alkaloids and (+)-Vinblastine 4 Selected Methodology 4.1 Ammonium Ylide Based [2,3]-Sigmatropic Rearrangements To Form Natural Product Cores 4.2 Cascade Reactions Involving [1,2]-Stevens Rearrangement/ Hofmann-Type Elimination Events 5 Conclusions