1,4‐Dithianes in Synthesis: Rapid Assembly of Indolizidine Alkaloid‐Type Scaffolds Through Cationic Polyene Cyclization

We report a synthetic approach to the indolizidine scaffold, fused to a 1,4‐dithiane. In a straightforward three‐step protocol, the commercially available building block 5,6‐dihydro‐1,4‐dithiin‐2,3‐dicarboximide undergoes two consecutive alkenylations, followed by a cationic cyclization mediated by an α,β‐unsaturated N ‐acyliminium ion, affording a small range of substituted indolizidine scaffolds. The reaction was originally observed as an unexpected side reaction, but offers an attractive entry into this class of biologically active alkaloids.