Under copper(I) or silver(I)/base cocatalysis conditions, transient 2H-pyrroline intermediates generated by the cycloaddition of isocyanoacetates and olefins can be in situ subjected to further transformations. A strategically novel, convergent, mild, efficient, general and atom-economic access to cis-3a,8a-hexahydropyrroloA C H T U N G T R E N N U N G [2,3-b]indoles, which are core scaffolds in many biologically important natural products, has been developed based on this concept.