ChemInform Abstract: Ring Expansion of 2‐(α‐Hydroxyalkyl)azetidines: A Synthetic Route to Functionalized Pyrrolidines.

Abstract

Pyrrole derivatives R 0120Ring Expansion of 2-(α-Hydroxyalkyl)azetidines: A Synthetic Route to Functionalized Pyrrolidines. -Activation of the hydroxy moiety in the azetidine substrates is achieved with thionyl chloride following A) and B) or by mesylation. They undergo ring expansion when subjected to the conditions shown in the scheme. -(DURRAT, F.; VARGAS SANCHEZ, M.; COUTY*, F.; EVANO, G.; MARROT, J.; Eur. J. Org.

Diastereoselective ring cleavage of azetidines with cyanogen bromide

“…1 When the nitrogen atom within this heterocycle is not acylated or tosylated, the nucleophilic character, as well as the basicity, of the intracyclic amine is close to a linear amine, in contrast to aziridines where the basicity is considerably lower. Therefore, N-alkyl azetidines react with many electrophiles (eg chloroformates, 2 alkyl halides, 3 alkyl sulfonates, 4 triphosgene, 5 cyanogen bromide 6 ) to give a stable or transient azetidinium ion that can react further either by ring cleavage or by ring-expansion. 7 In this area, it was recently reported 8 (Scheme 1A) that C-3 substituted azetidiniums can be opened in an enantioselective manner in the presence of a catalytic amount of a SPINOL-derived phosphonate acting as a chiral counteranion for the azetidinium cation.…”