Intramolecular capture of pummerer reaction intermediates by an aromatic nucleophile: selective construction of 1,4-benzothiazine and indole ring systems.
The simple alkyl sulfoxide 6 carrying two aromatic nucleophiles, when treated with trifluoroacetic anhydride at room temperature (Pummerer reaction conditions), underwent an intramolecular aromatic sulfenylation of the 6-exo-tet process in an exclusive manner to yield two regioisomeric 1,4-benzothiazine derivatives, 8 and 9. On the other hand, a similar reaction of the alpha-acyl sulfoxide 7, possessing identical aromatic nucleophiles, caused an intramolecular aromatic alkylation of the 5-exo-trig process to produce the 3-oxo-indole derivative 14 in a quantitative yield. These results demonstrate that the construction of 1,4-benzothiazine and indole ring systems can be achieved in a selective manner by proper choice of the sulfoxide side chain.
Horiguchi
Y
Y
Showa Pharmaceutical University, Machida, Tokyo, Japan.
Sonobe
A
A
Saitoh
T
T
Toda
J
J
Sano
T
T
D000089:Acetic Anhydrides; D000478:Alkylation; D003500:Cyclization; D005663:Furans; D007202:Indicators and Reagents; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D007546:Isoquinolines / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D013843:Thiazines / Q000138:chemical synthesis* / Q000737:chemistry; D014025:Titanium / Q000737:chemistry
C446962:1,4-benzothiazine; D000089:Acetic Anhydrides; D005663:Furans; D007202:Indicators and Reagents; D007211:Indoles; D007546:Isoquinolines; D013843:Thiazines; C018674:tetrahydrofuran; D014025:Titanium