Studies On Selective Ring-opening Reations Of 1,2-epoxides Using Organic Reductants

The 1,2-epoxide functional groups are present extensively in nature. The ring-opening products of the 1,2-epoxide are powerful building blocks in organic synthesis. Besides a concise review on the new progress made in this field in recent years, this thesis focuses on synthetically useful ring-opening reactions of 1, 2-epoxides by employing organic reducing agents. The results are obtained as following:1. Hantzsch 1,4-dihydropyridine, an analogue of NAD(P)H, was develped as an efficient reduing agent in reductive cyclization of 2-nitrophenoxymethyloxiranes. In the presence of Pd/C as a catalyst, the tandem reduction and intramolecular 1, 2-epoxide opening of substituted 2-nitrophenoxymethyloxiranes gave corresponding 2H-1,4-benzoxazine, a structural subunit of many naturally occurring compounds. It was the first application of model compounds of coenzyme NAD(P)H in the synthesis of oxazinic series.2. A facile visible light photocatalysis system was employed to transformation ofα,β-epoxyketones toβ-hydroxyketones. Under irradiation by a 15 W fluorescent lamp with Tris(2,2'-bipyridyl)ruthenium(II) hexafluorophosphate as a catalyst, the photoinduced electron transfer reaction from ethyl diisopropyl amine to a,β-epoxyketones took place smoothly and producdβ-hydroxyketones in high yields.