Sequenced reactions with samarium(II) iodide. A complementary annulation process providing access to seven-, eight-, and nine-membered carbocycles

Samarium(II) iodide promotes an efficient one-pot annulation reaction betwe en omega-iodo esters and 2-(omega-chloroalkyl)cycloalkanones. An initial in termolecular carbonyl addition reaction between the iodo ester and the keto ne generates a lactone intermediate. The lactone undergoes a subsequent nuc leophilic acyl substitution reaction with an organosamarium derived from th e chloride. Nickel(II) iodide is an efficient catalyst for the first step o f the process, and light is utilized to promote the second step. Seven-, ei ght-, and nine-membered rings can be accessed by this sequential dianionic process. This annulative approach to carbocycles is complementary to previo usly reported procedures.