ChemInform Abstract: Silver‐Catalyzed Tandem Ammonolysis—Cyclization of 2‐Alkynylbenzenamines with Tetraalkylthiuram Disulfides to 4‐Methylene‐4H‐benzo[d][1,3]thiazin‐2‐amines.

Abstract

Silver-Catalyzed Tandem Ammonolysis-Cyclization of 2-Alkynylbenzenamines with Tetraalkylthiuram Disulfides to 4-Methylene-4H-benzo[d][1,3]thiazin--2-amines. -Disulfides (IIa) and (IIb) afford exclusively the (Z)-products on reaction with substrate (Ia/Ib). The dimethyl analogue reacts similarly, when the thiophene (Ic) is used. Generally, mixtures are obtained with (IIc) where the (Z) isomer is the main component. Substrates with an alkyl substituent at the alkyne chain [cf. (XII) and (XIV)] are not effective. In the case of aniline (XVII) bearing an electron-withdrawing aryl group, more drastic conditions are necessary and the yield is relatively low. -(TANG, R.-Y.; LUO, P.-S.; ZHANG, X.-G.; ZHONG, P.; LI*, J.-H.; Synlett 2010, 9,

Tandem addition-cyclization reaction catalyzed by ytterbium chloride: An efficient one-step synthesis of 2-amino-4H-3,1-benzothiazine

“…As a consequence, several approaches to prepare 2-amino-4H-3,1-benzothiazines have been reported [1831], and most of which are based on the reactions of aromatic amines or thioureas bearing a halomethyl or hydroxymethyl substituent in the ortho position of the aromatic ring. We noticed that a strong Bronsted acid [1822] or noble metal catalyst [23,24] was required for a smooth reaction in most cases. At the same time, heating under reflux in organic solvents, complex and inaccessible substrates, and multistep reaction processes appeared to be essential conditions to obtain satisfactory results.…”