Pyrrolidino(or isoindolo)[1,3]benzothiazines 1a,b were efficiently synthesized in a four-step sequence from the known o-(benzylthio) benzyl alcohol 2. The key step was the nucleophilic attack of the sulfur atom onto N-acyliminium ion 6 which was generated in high acidic medium from omega-carbinol lactam 5. The last was regioselectively obtained by reduction of the parent imide 4. (C) 1994 Elsevier Science Ltd. All rights reserved.
π-Aromatic and Sulfur Nucleophilic Partners in Cationic π-Cyclizations: Intramolecular Amidoalkylation and Thioamidoalkylation Cyclization via ω-Carbinol Lactams<sup>1</sup><sup>,</sup><sup>2</sup>
作者:Nicolas Hucher、Bernard Decroix、Adam Daïch
DOI:10.1021/jo0156316
日期:2001.6.1
described. During this reaction, we have shown that omega-carbinol lactam precursor 14a led to endocyclic and exocyclic N-acyliminium ions 18a and 19a in equilibrium via the cyclic aza-sulfonium ion A. The latter furnished the expected products 20a and 21a in good yields. Similarly, different omega-carbinol lactams 14b-e substituted at C-angular position afforded the corresponding isoindolobenzothiazinones