Hasegawa Eietsu, Ishiyama Kenyuki, Fujita Takayuki, Kato Tomoyasu, Abe Toshiaki
Department of Chemistry, Faculty of Science, Niigata University, Ikarashi, Niigata 950-21, Japan.
J Org Chem. 1997 Apr 18;62(8):2396-2400. doi: 10.1021/jo9622439.
Photoreaction of trans-1-(4-cyanophenyl)-3-phenyl-2,3-epoxy-1-propanone (trans-4'-cyanochalcone epoxide) with various electron donors was studied. Irradiation of this epoxy ketone with amines produced 1-(4-cyanophenyl)-3-phenyl-1,3-propanedione and 1-(4-cyanophenyl)-3-hydroxy-3-phenyl-1-propanone in various ratios depending on the kinds of amine and solvent used. A reaction mechanism involving an amine cation radical-assisted rearrangement of the epoxy ketone anion radical was proposed to be most consistent with the marked change in the yield of beta-diketone. On the other hand, the timing of proton transfer to the anionic intermediates is considered to be a key factor to yield the beta-hydroxy ketone. Information obtained from the photochemical study was useful to find the reaction conditions for the conversion of several aromatic epoxy ketones to hydroxy ketones by the use of samarium diiodide. Addition of methanol significantly changed the product distribution. Proper choice of water or methanol as a proton source produced hydroxy ketones in moderate to good yields.
研究了反式-1-(4-氰基苯基)-3-苯基-2,3-环氧-1-丙酮（反式-4'-氰基查尔酮环氧化物）与各种电子供体的光反应。用胺照射这种环氧酮，根据所用胺的种类和溶剂的不同，会以不同比例生成1-(4-氰基苯基)-3-苯基-1,3-丙二酮和1-(4-氰基苯基)-3-羟基-3-苯基-1-丙酮。提出了一种涉及胺阳离子自由基辅助环氧酮阴离子自由基重排的反应机理，这与β-二酮产率的显著变化最为一致。另一方面，质子转移到阴离子中间体的时机被认为是生成β-羟基酮的关键因素。从光化学研究中获得的信息有助于找到使用二碘化钐将几种芳香族环氧酮转化为羟基酮的反应条件。加入甲醇会显著改变产物分布。适当选择水或甲醇作为质子源，可以中等至良好的产率生成羟基酮。
