Synthesis of Substituted Cyclooctanols by a Samarium(II) Iodide Promoted 8-Endo Radical Cyclization Process

Evidence for Ionic Samarium(II) Species in THF/HMPA Solution and Investigation of Their Electron-Donating Properties

“…This led to E8 À 1.79 AE 0.08 V versus SCE (À 2.31 AE 0.08 V versus Fc /Fc) and to log k8 [cm s À1 ] À 5.8 AE 0. 7. This E8 value differs by only 40 mV from that determined in a recent study, [10b] although the simulation procedure used therein was based on the model proposed for the SmI 2 /SmI 2 system [3] with an equilibrium process incorporated as a homogeneous follow-up reaction.…”

“…[2,4] Other effects observed when this cosolvent is used include an increase in the stability of the organosamarium species formed, allowing reactions to be performed under Grignard conditions, [5] enhancement of stereoselectivities, [5c, 6] and promotion of certain radical cyclizations. [6,7] Recently, resolution of the crystal structures of [SmI 2 (hmpa) 4 ] and [Sm(hmpa) 6 ] 2 2 I À showed that both reside in an octahedral configuration. [8] The short SmÀO bonds (2.5 ) suggest that the electron-donating ligands are strongly bonded to the lanthanide ion, and thus explain its enhanced reducing power.…”

Intramolecular carbolithiation promoted by a DTBB-catalysed chlorine–lithium exchange

“…31 When (Z)-6-chloro-1-phenylhex-1-ene (15) was lithiated under DTBB-catalysis, we always obtained the cyclised products 17 either at 278 or at 2308C, so after the first chlorine -lithium exchange a carbolithiation took place to yield the intermediate 16, which by reaction with some electrophiles (E¼PhCHO, Et 2 CO, Me 3 SiCl) and final hydrolysis gave the mentioned products 17 (Scheme 5 and Table 6). At 2788C the reaction under Barbier-type conditions did not work (Table 6, entry 2).…”

Some Synthetic Uses of Double‐Bonded Functional Groups

“…The reaction is performed in THF in the presence of HMPT and occurs in good yield with excellent stereocontrol. If appropriately located carbonyl and alkene moieties are present in a molecule, then SmI 2 -HMPT can be used to form cyclooctanols by a radical cyclization process; in some cases there is a reasonable degree of diastereoselectivity (equation 138) 521 …”