Catalyst‐Free [3+2] Cycloaddition of Isoquinolinium/Pyridinium Ylides and Electron‐Deficient Alkenes

Abstract

The development of simple‐to‐operate methods for the preparation of indolizidine derivatives are of great importance. A mild one‐pot protocol for the [3+2] cycloaddition of isoquinolinium/pyridinium ylides and electron‐deficient alkenes using NaBH3CN as reductant has been developed. The protocol has a broad substrate scope (more than 40 examples) and provides various novel hexahydroindolizidine derivatives in high yields and excellent diastereoselectivities (up to >20/1).

Chiral π–Cu(ii)-catalyzed site-, exo/endo-, and enantioselective dearomative (3 + 2) cycloadditions of isoquinolinium ylides with enamides, dienamides, and a trienamide

“…In recent years, bench-stable isoquinolinium ylides ( 1 ) have garnered significant attention in synthetic organic chemistry due to their efficiency in the construction of pyrroloisoquinoline scaffolds, which are crucial structural motifs in various natural products and pharmaceutically active compounds. 8 However, only a few examples for their use as dipolar compounds in dearomative (3 + 2) cycloaddition reactions have been reported so far. 7 l ,8 e Therefore, the development of a catalytic enantioselective (3 + 2) cycloaddition reaction of 1 with α,β-enamides ( 2 ) for the construction of pyrroloisoquinoline derivatives ( 3 ) would be of considerable significance.…”