A Straightforward Synthesis of Benzothiazines

Abstract

A series of 4H-3,1-benzothiazines have been successfully synthesized through a three-step sequence starting from commercially available 2-iodoaniline. The key step consists of the cyclization of compounds 6 via an intramolecular S-conjugate addition. The synthesis is straightforward, gives good yields and offers a broad range of possibilities since R can be many alkyl or aryl groups and Z a suitable electron-withdrawing functionalization.

Synthesis and Anticancer Activity of New 2‐Aryl‐4H‐3,1‐benzothiazines

“…Recently, a series of 4 H ‐3,1‐benzothiazines has been successfully synthesized in a three‐step sequence starting from commercially available 2‐iodoaniline. The key step consists of the cyclization via an intramolecular S‐conjugate addition 18. An efficient path to enantiopure 1,3‐benzothiazines has been elaborated by the reaction of cyclic sulfenamides and alkylpropiolates or tosylacetylenes catalyzed by cesium fluoride 19.…”

New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence

“…neuroprotective [10], antiproliferative and antifungal activities [11]. Due to the significant bioactive properties of the 3,4-dihydroquinazoline and 4H-3,1-benzothiazine moieties, many preparation procedures have appeared in the literature for the synthesis of their derivatives [12][13][14][15][16][17][18][19][20][21][22]. For example (Scheme 1), a one-pot Tf 2 O-mediated assembly of amides, amines, and ketones provided 3,4-dihydroquinazolines in good yields via successive triflic anhydride-mediated amide dehydration, ketimine addition, and Pictet-Spengler-like cyclization processes [12].…”

“…Other 3,4-dihydroquinazolines were also obtained efficiently by intramolecular aza-Wittig reactions [ 14 ]. Some 4 H -3,1-benzothiazines were prepared by intramolecular thia-Michael addition with broad reaction scopes [ 19 ]. The rearrangement of 2-isothiocyano triarylmethanes in the presence of AlCl 3 were also used for the synthesis 2,4-diaryl-4 H -3,1-benzothiazines through aromatic ring transfer [ 20 ].…”

Microwave‐assisted Solid‐phase Synthesis of N‐substituted‐2‐aminobenzo[d][1,3] Thiazine Derivatives from a BOMBA Resin

“…The most general method for the synthesis of benzo[ d ]thiazine is the reaction between o ‐aminobenzyl chlorides and different thiocarboxamides benzopyran‐2‐thiones or thiourea . Furthermore, Vallribera reported the method using commercially available 2‐iodoaniline through three‐step sequence including the key step of cyclization via an intramolecular S‐conjugate addition . Recently, an enantioselective synthesis of such benzothiazines has been explored by Harmata and Hong .…”