A highly efficient and convenient protocol was developed to access 2-amino-4H-benzothiopyran-4-ones through a process of conjugated addition–elimination. The sulfinyl group was proved to be the optimum leaving group by thorough investigations on the elimination of sulfide, sulfinyl, and sulfonyl groups at the 2-position of benzothiopyranone. Most 2-aminobenzothiopyranones were obtained in good to excellent yields under refluxing in isopropanol within 36 h. This method is base-free and the substrate scope in terms of electronic properties of the substituents of the benzothiopyranone is broad. The ten grams scale-up synthesis of the representative compounds 4a and 4d was implemented to show the practical application of this reaction, which afforded the corresponding compounds in good yields and excellent chemical purity without requiring column chromatographical purification.
开发了一种高效便捷的协同加成-消除过程,以访问2-氨基-4H-苯并硫杂吡喃-4-酮。经过对苯并硫杂吡喃酮2位的硫醚、亚砜和磺酰基团消除的彻底研究,证明亚砜基团是最佳的脱离基团。在异丙醇中回流36小时内,大多数2-氨基苯并硫杂吡喃酮以良好至优异的产率获得。该方法无需碱,对苯并硫杂吡喃酮取代基的电子性质具有广泛的底物范围。以代表性化合物4a和4d进行了十克级合成,展示了该反应的实际应用,获得了相应的化合物,并具有良好的产率和优异的化学纯度,无需进行柱层析纯化。