Synthesis And Functionalization Of Highly Substituted Furans

Furans, the important five-membered heterocyclics, play an important role inorganic chemistry due to their presence as key structural units in many naturalproducts as well as numerous pharmaceuticals. A variety of compounds with furanrings have been used as flavor, fragrance substances, insecticides, and antileukemicagents. Although a lot of methodologies for the synthesis of polysubstituted furanshave been reported, an efficient and straightforward route to highly functional furansunder mild reaction conditions also remains an important research theme in organicchemistry.In the first part, we focused our attention on CuI-mediated iodocyclization ofcyclopropylideneallenyl ketones to afford highly substituted furan derivatives. Firstly,we used3-cyclopropylidene-1,2-diphenylprop-2-en-1-one as an example to optimizeof the reaction conditions. With the optimized conditions in hand, we prepared avariety of cyclopropylideneallenyl ketones and set out to explore the generality of thismethod. We found all substrates could achieve good to excellent yields. Then, theplausible mechanism for this reaction was proposed. Finally, the resulting productswere synthetically useful for amplification of molecular complexity to access furanderivatives with more advanced structures via nucleophilic substitution reactions andsuzuki cross-coupling reactions.In the second part, we introduced the functionalities of furans and somesynthetical approaches to stable enols. At first, we used furan-2-yldiphenylmethanoland3-oxo-N-phenylbutanamide under the catalyst of Lewis acid to research (Z)-2-(5-benzhydrylfuran-2-yl)-3-hydroxy-N-phenylbut-2-enamide. Then, we optimized theconditions from Lewis Acids, solvents, temperatures and so on. After ascertaining theoptimal condition, we extended the substrates to gain the products in good to excellentyields. In order to verify whether the enols are stable in CDCl3, we stored the furanenol in CDCl3for8days and found the quantities of H at chemical shifts δ=6.26andδ=6.38respectively never change as time went on from the1H NMR spectrum, whichmeant the furan enols were stable, and the Kenol>25. Finally, we developed someapplications using the stable furan enols to form the substituted furan containningquaternary carbon atom via nucleophilic substitution reactions.