A novel synthesis of 1,2,3,4-tetrahydroquinolines via Pummerer-type reaction of N-aryl-N-[(phenylsulfinyl)propyl]formamide

Article abstract of DOI:10.1248/cpb.47.1269

A synthesis of 1,2,3,4-tetrahydroquinolines (TQs) 13 with two and three methoxyl groups on the benzene ring, was achieved via intramolecular cyclization of N-aryl-N-[(phenylsulfinyl)propyl]formamides 7 utilizing the Pummerer reaction as a key step. The reaction was carried out by using trifluoroacetic anhydride (TFAA) (method A) or TFAA-BF₃ · Et₂O (method B). The cyclization to 4-PhSTQs 8 proceeded effectively when the reaction center at the benzene ring was electronically activated by a methoxyl group. In the reaction of sulfoxide 7e having two OMe groups in the ortho- and para- positions, a different cyclization reaction leading to 1,5-benzothiazepine derivative 9 was observed, indicating that the high nucleophilicity of the benzene ring caused the unexpected reaction prior to cyclization to 4-PhSTQs 8. This route starting from methoxyanilines provides an efficient and convenient method of TQ synthesis.

Full text of DOI:10.1248/cpb.47.1269

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