Paper
Lewis acid-mediated reactions of 1-cyclopropyl-2-arylethanone derivatives with allenic ester, ethyl acetoacetate, and methyl acrylate.
Published Jun 21, 2008 · M. Shi, Xiangying Tang, Yong‐Hua Yang
The Journal of organic chemistry
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Abstract
TMSOTf-mediated reactions of 2-aryl-1-(1-phenylcyclopropyl)ethanones 1 with allenic esters afford a novel method for the synthesis of 6-methyl-3a,7-diaryl-3,3a-dihydro-2H-benzofuran-4-one derivatives 2 in moderate yields. In addition, we also found that TMSOTf-mediated reactions of 1-cyclopropyl-2-arylethanones with ethyl acetoacetate can provide the corresponding 2,3-dihydrobenzofuran-4-ol and dihydrofuro[2,3-h]chromen-2-one in moderate yields via a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H2O, one intermolecular aldol type reaction and two intramolecular aldol type reactions, a cyclic transesterification, dehydration, and aromatization. Moreover, by using methyl acrylate to replace allenic ester, the corresponding 7-aryl-3,5,6,7-tetrahydro-2H-benzofuran-4-one and 5-aryl-3,5,6,7-tetrahydro-2 H-benzofuran-4-one can be formed in moderate to high yields in the presence of Bi(OTf)2Cl. Plausible reaction mechanisms have also been provided on the basis of control experiments.
TMSOTf-mediated reactions of 1-cyclopropyl-2-arylethanone derivatives with allenic esters, ethyl acetoacetate, and methyl acrylate enable the synthesis of 6-methyl-3a,7-diaryl-3,3a-dihydro
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