A novel tandem reaction of 3-substituted coumarins with two equivalents of dimethylsulfoxonium ylide to 2-substituted cyclopenta[b]benzofuran-3-ol derivatives
摘要:
When the coumarins (4) having an electron-withdrawing group at the 3 position were treated with 2.4 equiv. of dimethylsulfoxonium methylide at room temperature in DMF or DMSO, novel tricyclic 2-substituted cyclopenta[b]benzofuran-3-ols (5) were obtained in moderate to good yields. The intermediates, la-substituted benzo [b] cyclopropa [d]pyran-2(1aH)-ones (3), of this tandem reaction were isolated and derived to the corresponding 2-substituted cyclopenta[b]benzofuran-3-ols (5) by treatment with 1.1 equiv. of dimethylsulfoxonium methylide. (C) 2002 Elsevier Science Ltd. All rights reserved.
Stereospecificity of Diels–Alder Reactions Validated Using Ab Initio Calculations: Synthesis of Novel Coumarin and Phenanthridine Derivatives
作者:A. El-Shafei、A. A. Fadda、I. I. Abdel-Gawad、E. H. E. Youssif
DOI:10.1080/00397910802711326
日期:2009.7.21
A new series of coumarin derivatives (2-5) was synthesized by reaction of phenylsulfonylacetonitrile (1) with 2-hydroxy-1-naphthaldehyde and/or salicyaldehyde. Compounds 3 and 5 were converted to the corresponding phenanthridine analogs 6 and 7, respectively. Compound 9a was treated with different dienophiles to furnish the endo adducts of compounds (11a-d) rather than the exo adducts. Ab initio calculations at the Hartree-Fock (HF) level using the basis set 6-31G (d,p) was used to study and validate the stereospecificity of compounds 11a-d and showed clearly that the endo adducts were thermodynamically favorable. PM3 parameters also showed that the endo adducts are thermodynamically and kinetically favorable. Tetrahydrobenzochromenone (11) was synthesized and allowed to react with different aromatic diazonium salts to give the corresponding 4-arylazo derivatives (13), which were converted to the corresponding diazaindenophenanthrene derivatives (14) by reaction with o-diamines.