Synthesis Of Cyclopropanes And Their Applications In The Synthesis Of Nitrogen-containing Heterocycles

The chemistry of three-membered rings has come a long way in the past 100 years, since the first cyclopropane derivatives were synthesized by William Henry Perkin in Munich in the laboratory of the eminent chemist Adolf von Baeyer. But at that time, Cyclopropanone chemistry had not been received considerable attention. In the beginning, Most of the simple cyclopropane derivatives are actually prepared by such 1,3-elimination reactions. A great advance in the synthesis of cyclopropanes was initiated with the discovery of carbene additions to alkenes. In addition, the advance is mainly due to the rapid development of carbene chemistry, new photochemical and other strikingly simple transformation leading to three-membered carbocycles. As a result, almost any kind of cyclopropane derivatives structure appears to be achived in cyclopropane chemistry nowadays.Cyclopropanes are extremely versatile building blocks in organic synthesis owing to their ready accessibility and good reactivity. Since the first report by Cloke in 1929 that cyclopropyl ketones can be transformed into dihydrofuran derivatives, the synthetic applications of cyclopropyl ketones have been well studied. Their chemistry has been focus of intense research for decades, particularly in heterocyclic synthesis, and continues to be an active area of research today. The pyrrole, oxazoles, pyridinones and quinolines have been prepared from cyclopropanes. Comparatively the studies on the synthetic utility of cyclopropyl oximes are relatively few.Cyclopropyl oximes are a kind of versatile intermediates used in organic synthesis. Base on its structure, it is widely used in organic synthesis. In recent years, we have been devoting our efforts towards the synthesis and applications on cyclopropyl oximes and achieved some interesting results. This work is mainly based on the following three aspects:1. The synthesis of cycloropyl oximes.2. An efficient and divergent synthesis of fully substituted pyrazoles and isoxazoles is developed through cyclopropyl oximes, Combining with the special properties of cyclopropyl oximes.3. A convenient and efficient synthesis of spiro-fused pyrazolin-5-one N-Oxides is developed via the PIFA-mediated cyclization reactions of readily available 1-carbamoyl-1-oximylcycloalkanes. This protocol is associated with readily available starting materials, mild conditions, good yields, and broad range of synthetic potential of the products.In summary, a facile and convenient synthesis of heterocyclic compounds is developed via cyclopropyl oximes. The mild conditions, good yields, and broad range of synthetic potential of the products make this synthetic strategy much attractive.