The Study Of Synthesis Of Dihydrofuran Derivatives From 1-acetyl-N,2-diphenylcyclopropanecarboxamide Derivatives

Dihydrofuran derivatives as the important chemical units have presented in a large variety of naturally occurring bioactive substances . In addition, the utility of 2,3-dihydrofuran derivatives as organic intermediates in the synthesis of various organic heterocyclic compounds has been well recognized .Such utility can be realized through the cycloaddition reactions or the recyclisation reactions. The synthetic approaches for 2,3-dihydrofurans include [3+2] annulations,[4+1] annulations and the rearrangement of cyclopropylketones.The rearrangement of cyclopropylketones to corresponding 2,3-dihydrofuran derivatives is undoubfully an efficient methods for the construction of the dihydrofuran framework in organic synthesis. The 1-acyl-N-aryl cyclopropane- carboxamides as doubly activated cyclopropanes are under our ongoing research whose structure can be recognized as a kind of special cyclopropylketone. In this paper,we make some modification on the stracture of 1-acyl-N-aryl cyclopropane- carboxamides by introducing the phenyl as activing group to the cyclopropane in order to increase the ring-opening activity of the cyclopropane.The subsequent experiments confirm the high ring-opening activity of the modified cyclopropane and also indicate that such modified cyclopropanes can be transformed to corresponding 2,3-dihydrofuran derivatives in high yields in the Lewis acids-catalyzed situations .Furthermore,when exposed in the srong Bronsted acids such as concentrated sulfuric acid,they can be transformed to another kind of 2,3-dihydrofuran derivative or furoquinoline derivatives. Such high ring-opening activity of the modified cyclopropane can be ascribed to the existence of the phenyl substituent.In this paper ,we have examined the reaction behaviors of 1-acetyl-N 2-diphenyl–cyclopropane-carboxamides in the acids-catalyzed situation by conducting series of experiments , presenting the plausible mechanism and determining its applicability in the synthesis of dihydrofuran derivatives .