Formal [3+2] Annulation Involving Allylic Bromides and Thioureas. Synthesis of 2‐Iminothiazolidines through a Base‐Catalyzed Intramolecular anti‐Michael Addition

Abstract

A simple and efficient protocol was developed for the synthesis of 2-iminothiazolidines through a base-mediated [3+2] annulation involving substituted thioureas and allylic bromides bearing electron-withdrawing groups. This domino process consists of nucleophilic displacement, followed by intramolecular anti-Michael addition of the preformed allylic isothiourea under mild conditions to give the thiazolidine core.

Expedient Synthesis of 2‐Iminothiazolidines via Telescoping Reactions Including Iron‐Catalyzed Nitrene Transfer and Domino Ring‐Opening Cyclization (DROC)

“…Among them, Sá et al . have described a base‐mediated [3+2] annulation involving allyl bromide and N‐acylthioureas (Scheme 1a) [4] . Alper et al .…”

“…Among them, Sá et al have described a base-mediated [3 + 2] annulation involving allyl bromide and N-acylthioureas (Scheme 1a). [4] Alper et al have reported a rhodium-catalyzed synthesis of thiazolidine using carbodiimides (Scheme 1b). [5] But one of the most promising routes is the domino ring-opening cyclization (DROC) of aziridines with isothiocyanates (Scheme 1c).…”

One‐Pot Synthesis of α‐Diazo‐γ,δ‐unsaturated Esters as Versatile Building Blocks for Functionalized Dienes, Cyclopentenes, and 5,7‐Fused Bicycles

“…Motivated by these preliminary results with both DBU and NaOH, and being aware that the preparation [18] of substrate 1 a involves a straightforward NaOH-mediated allylation of ethyl acetoacetate (4) with functionalized allylic bromides 5 derived from Morita-Baylis-Hillman adducts, [19,20] we envisioned that the two steps (allylation followed by the deacylative diazo transfer reaction) could be adapted to a one-pot method. Therefore, the α-diazo-γ,δ-unsaturated ester 2 a was readily prepared from allylic bromide 5 a in aqueous alkaline medium, as presented in Scheme 2.…”

FeCl3‐Catalyzed [3+2] Cycloaddition Reaction: A Mild Synthetic Approach to Spirooxindolo‐2‐iminothiazolidine Scaffolds

“…Ferreira and co‐workers have reported a domino reaction for the synthesis of 2‐iminothiazolidines from acylthioureas and allylic bromides bearing electron with‐drawing groups via a base‐mediated [3+2] cycloaddition strategy . Nevertheless, the previous protocols have some inherent limitations such as long reaction time, harsh reaction conditions, tedious work‐up, low yields, etc .…”