Highly Z‐Selective Synthesis of Highly Substituted 1,3‐Oxathiolane‐2‐imines via TfOH‐Catalyzed Formal [3+2] Cycloaddition of Donor‐Acceptor Oxiranes and Isothiocyanates

Abstract

TfOH-catalyzed [3 + 2] cycloaddition of donor-acceptor oxiranes with isothiocyanates via chemoselective CÀ O bond breakage of DÀ A oxiranes was developed under metal-and additive-free conditions. This method providing a facile access to a diverse range of highly substituted 1,3-oxathiolane-2-imines in good to excellent yields and with high Z-selectivity and excellent functional group tolerance. In addition, the established protocol can be easily scaled up to gram level in excellent yield. Furthermore, transformation of cycloadduct into 1,3-oxathiolane-2-one by acid hydrolysis of the imino group is easily achieved in moderate yield.

Highly Chemoselective Synthesis of Purino[3,2-c]oxazoles via the Asymmetric Dearomative [3+2] Cycloaddition of Purines with Donor–Acceptor Oxiranes

“…Over the past few years, the methodology of [3+2] cycloaddition reactions of carbonyl ylides has also significantly progressed . For instance, the 1,3-dipolar [3+2] cycloaddition reaction between unsaturated double bonds and the carbonyl ylides produced by the C–C bond cleavage of ethylene oxide can be used to synthesize structurally diverse five-membered ring compounds. − …”

“…Products of this reaction have included polysubstituted furan rings, 1,3-dioxolanes, polysubstituted oxazolidines, and polysubstituted thiazoles . Nonetheless, there are only three reports of dearomatization reactions of donor–acceptor (D–A) oxiranes with heterocyclic compounds .…”