“…The ability to employ an unactivated C3 À C4 olefin as the nucleophile in the second cyclization is likely a result of the enhanced electrophilicity at C2 of intermediate 6 imparted by the chlorine atom, [19] together with a high resilience of 6 toward an undesired Pictet-Spengler rearrangement. [20,21] Consistent with the sensitivity of this doublecyclization step, the use of less-basic 2-chloropyridine or more-nucleophilic pyridine as the additive gave the desired diiminium ion 5 with reduced efficiency as evidenced by the presence of singly cyclized side products, recovered starting material, and significant decomposition. [22] The synthetic versatility of diiminium ion 5 is illustrated by its conversion into alkaloids (À)-1, (+)-2, and (À)-17 (Scheme 3).…”