Samarium(II)‐Promoted Cyclizations of Non‐activated Indolyl Sulfinyl Imines to Polycyclic Tertiary Carbinamines

Samarium(II)-promoted cyclizations of N-acylated indolyl sulfinyl imines without electron-withdrawing groups at C-3 furnished tertiary carbinamines in good yield. Screening the reaction conditions revealed that application an excess samarium diiodide presence water and lithium bromide provided cleanest reactions highest yields. The most striking observation during this investigation was reductive detachment sulfur functional group, which likely precedes cyclization step. As consequence no enantioselectivity could be observed if enantiopure were employed. mechanisms N−S cleavage intermediate as well role additives are discussed. presented method generates interesting polycyclic indoline derivatives; a cascade involving ethoxycarbonyl-substituted side-chain unique tetracyclic spiro-γ-lactams.