New methods and reagents in organic synthesis. 35. A new synthesis of some non-steroidal anti-inflammatory agents with the 2-arylpropionic acid skeleton by the use of diphenyl phosphorazidate (DPPA) as a 1,3-dipole.
作者:NOBUTAKA KAWAI、NOBUHARU KATO、YASUMASA HAMADA、TAKAYUKI SHIOIRI
DOI:10.1248/cpb.31.3139
日期:——
Reaction of diphenylphosphinic azide (8) with the pyrrolidine enamine 13 of 4-isobutylpropiophenone afforded two amidines 15a and 16a, which were derived from the 1, 3-dipolarcycloadduct 14a by the expulsion of nitrogen followed by 1, 2-aryl migration (path a) and by 1, 3-dipolar elimination (path b), respectively. Although diphenylthiophosphinic azide (9) and ethyl phenylthiophosphonoazidate (10) also gave similar results, diphenyl phosphorazidate (DPPA, (C6H5O)2P(O)N3) furnished the amidine 15d formed via path a as the sole isolable product. Hydrolysis of 15d with potassium hydroxide afforded ibuprofen (3) in good yield. Other nonsteroidal antiinflammatory agents, naproxen (4), ketoprofen (5), and flurbiprofen (6), were analogously and conveniently prepared from the ketones 17, 22, and 25, respectively, by a similar three-step operation using pyrrolidine, DPPA, and potassium hydroxide. 2-(2-Dibenzofuranyl)-propionic acid (7) was also prepared from the ketone 28 by the three-step procedure.
二苯基膦氮酸氟(8)与4-异丁基苯丙酮的吡咯烷烯胺(13)反应,生成两个脒(15a和16a),它们分别是由1, 3-偶极环加成物(14a)通过排氮后发生1, 2-芳基迁移(路径a)和1, 3-偶极消除(路径b)而衍生得到的。虽然二苯基硫代膦氮酸氟(9)和乙基苯硫代膦酰基叠氮酸酯(10)也得到类似结果,但二苯基膦酰叠氮(DPPA, (C6H5O)2P(O)N3)仅通过路径a合成了可分离的唯一产物脒(15d)。用氢氧化钾水解15d,以良好产率得到布洛芬(3)。其他非甾体抗炎药物,萘普生(4)、酮洛芬(5)和氟比洛芬(6),分别通过类似的三步操作,使用吡咯烷、DPPA和氢氧化钾,从酮(17、22和25)方便地制备。通过三步法,从酮(28)也制备了2-(2-二苯并呋喃基)丙酸(7)。