Gold-Catalyzed 1,3-Thiazine Formation and Uncommon Tautomer Isolation

Abstract

This work represents the first example of a gold-catalyzed formation of 1,3-thiazine/1,3-thiazinane by means of a catalytic approach and further uncommon isolation of the two tautomers. The developed protocol gives rise to a broad scope of 1,3-thiazine derivatives with excellent yields in short reaction times. Interestingly, different isomers could be obtained depending on the state of the compound, and in the crystal state the 1,3-thiazinane isomer is obtained, while in solution the 1,3-thiazine is the unique isomer. This work represents an interesting approach for the synthesis of potential biologically relevant molecules and a crucial precedent in tautomerism isolation and characterization.

Transition‐Metal‐Free One‐Pot [3+3] Heteroannulative Coupling of Thioamides with Epichlorohydrin: Access to Diverse 1,3‐Thiazinanes

“…Zhai and co‐workers [6c] reported synthesis of 3,4‐dihydro‐2 H ‐1,3‐thiazines from α‐enolic dithioesters and 1,3,5‐triazinanes by tandem [3+3] annulation. Recently, Gimeno and co‐workers [6d] reported gold‐catalyzed formation of 1,3‐thiazine/1,3‐thiazinane by means of a catalytic approach (Scheme 1). However, these methods require a sequence of steps to get the core skeleton, suffer from a limited number of available starting materials for diversity synthesis or some other sustainability issues such as high cost of reaction and use of modified starting materials.…”