Fluorine‐Directed Diastereoselective Iodocyclizations

Synthesis of 3‐Fluoropyrrolidines and 4‐Fluoropyrrolidin‐2‐ones from Allylic Fluorides

“…We opted for the development of a new synthetic route using allylic fluorides as starting materials. In 2008, our group reported that fluorinated tetrahydrofurans and γ‐lactones are accessible upon iodocyclisation of allylic fluorides bearing a pending oxygen nucleophile 14. In these reactions, the fluorine substituent is an effective syn ‐directing group, a stereochemical preference dictated by an “inside fluoro effect ” .…”

Stereoselective Strecker and Carbamate Annulation Methodology for the Synthesis of 1‐Amino‐1,2,5‐trideoxy‐2,5‐imino‐L‐iditol

“…Given that the primary iodide appears to be a key intermediate during the carbamate annulation (9a Ǟ [10a] Ǟ 11), it is the formation of the iodide that determines the diastereoselectivity of the reaction. Seminal work by Chamberlin et al, [33,34] and the more recent theoretical studies by Gouverneur and co-workers, [35] highlight the effects of the substitution pattern on I 2 -mediated electrophilic halocyclizations and the role that the allylic group has on influencing the diastereoselectivity of the reaction. The attack of the amine on the I 2 -alkene complex is thought to take place via a five-membered ring transition state in which the internal nucleophile approaches the double bond in an envelope conformation and follows a Bürgi-Dunitz-like trajectory.…”

A fast, efficient and stereoselective synthesis of hydroxy-pyrrolidines

“…This high diastereoselectivity can be explained by considering a transition state model originally proposed by Chamberlin et al [29][30][31] and more recent theoretical studies presented by Gouverneur and co-workers. 32 In these models, attack of the amine on the I 2 -ethylene complex is thought to take place via a five-membered ring transition structure in which the nitrogen approaches the double bond in an envelope conformation and follows a Bürgi-Dunitz-like trajectory 33 (Fig. 2).…”