Decarboxylative Isomerization of N-Acyl-2-oxazolidinones to 2-Oxazolines

Abstract

N-Acyl-2-oxazolidinones are ring-opened by lithium iodide and decarboxylated in the presence of a mild proton source. Further reaction with an amine base provides 2-oxazolines. The transformation is general for oxazolidinones unsubstituted in the 5 position and occurs under mild conditions (25-50 degrees C). These results complement the existing methods for this transformation by allowing lower temperatures and/or avoiding metal catalysts.

Synthesis of Chiral Selenazolines from N-Acyloxazolidinones via a Selenative Rearrangement of Chiral Cyclic Skeletons

“…During the course of our studies, we conducted the reaction with N -acyloxazolidinones and, unexpectedly, obtained selenazoline products (Figure , bottom). A similar transformation of N -acyloxazolidinones with lithium iodide and an amine had previously been reported for the synthesis of chiral oxazolines (Figure , top), but reports on the application to the synthesis of chiral selenazolines as well as thiazolines do not exist . Herein, we report a new route to chiral selenazolines via the reaction between chiral N -acyloxazolidinones, elemental selenium, hydrochlorosilanes, and amines.…”

“…In addition, a racemization was not observed at the chiral center of the aminoalcohol moiety of the oxazolidinone under these reaction conditions in the reaction with enantiopure substrates ( R )- and ( S )- 1a . Addition of LiI, which is a key additive for previous oxazoline synthesis, did not affect the reaction efficiency at all.…”

An Exploration of the Metal Oxide-assisted Decomposition and Rearrangement of N-Acyl-1,3-oxazolidin-2-ones Leading to 2-Aryl-2-oxazolines [1]

“…Other published methods which facilitate ring formation via closure involving the oxazoline ring position C-5 carbon centre have shown that both inversion (for example: [38 -40, 43, 45 -47, 49]) or retention (e. g., [30,51]) of configuration can be mandated. The use of a small Bunsen burner flame here can be compared to such reactions under very high temperature conditions, such as those employed under FVP protocols [57]. The natural product Oxytri- phine (i. e., 2,5-diphenyl-2-oxazoline; Scheme 2: 8b) is an ideal candidate [58] to investigate the stereochemical outcome of the Mundy-Kim method as the optical properties of the enantiopure (5S)-(+) isomer are well-known [59].…”

“…In the field of chiral oxazoline synthesis, perhaps the best solvent-free method, and one that is rarely employed today, is the anhydrous Zn(OAc) 2 -mediated dehydration of N-acyl-β -hydroxyamines [30]. This method leads to enantiopure products with complete retention of configuration at both oxazoline ring positions C-4 and C-5 under solventless conditions and without the necessity of FVP temperatures [57].…”

A Useful Modification of the Evans Magnesium Halide Catalyzed anti-Aldol Reaction: Application to Enolizable Aldehydes

“…Reaction times (vis-à-vis conversion) should be carefully monitored. As the reaction mixtures age, small amounts of product from a secondary event, the decarboxylative isomerization of the N -acyloxazolidinone product ( 4 ) to 2-oxazolines ( 7 ) (via 5 and 6 , Scheme 2), 5 appear. As we previously have described, this process is catalytic in lithium iodide and triethylammonium ion present in the mixture accelerates the decarboxylation.…”