Ga. Molander et F. Machrouhi, Sequenced reactions with samarium(II) iodide. A complementary annulation process providing access to seven-, eight-, and nine-membered carbocycles, J ORG CHEM, 64(11), 1999, pp. 4119-4123
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.