One-Pot Syntheses of 2-(2-Sulfanyl-4H-3,1-benzothiazin-4-yl)acetic Acid Derivatives via Reactions of 3-(2-Isothiocyanatophenyl)prop-2-enoic Acid Derivatives with Thiols or Sodium Sulfide

✍ Scribed by Shuhei Fukamachi; Hisatoshi Konishi; Kazuhiro Kobayashi

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: German
• Weight: 159 KB
• Volume: 94
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.201000340

✦ Synopsis

Abstract

Two efficient methods for the preparation of 2‐(2‐sulfanyl‐4__H__‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 3 under mild conditions have been developed. The first method is based on the reaction of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoates 1a–1c with thiols in the presence of Et~3~N in THF at room temperature, leading to the corresponding dithiocarbamate intermediates 2, which underwent spontaneous cyclization at the same temperature by an attack of the S‐atom at the prop‐2‐enoyl moiety in a 1,4‐addition manner (Michael addition) to give 2‐(2‐sulfanyl‐4__H__‐3,1‐benzothiazin‐4‐yl)acetates in one pot. The second method involves treatment of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoic acid derivatives 1b–1d with Na~2~S leading to the formation of 2‐(2‐sodiosulfanyl‐4__H__‐3,1‐benzothiazin‐4‐yl)acetic acid intermediates 5 by a similar addition/cyclization sequence, which are then allowed to react with alkyl or aryl halides to afford derivatives 3. 2‐(2‐Thioxo‐4__H__‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 6 can be obtained by omitting the addition of halides.