A new method for faster and simple preparation of 3,3',4,4'-tetrahydro-3,3'-disubstituted-4,4'-biscoumarins with participation of an organozinc reagent is reported. The reaction is promoted by ultrasound irradiation and it offers a simple experimental setup and excellent reproducibility of the results. Moreover, homodimers were isolated in yields of 45⁻92%. The dimerization conditions are applicable
A New and Efficient Method for the Synthesis of 3,4-Disubstituted Pyrrolidine-2,5-diones
作者:Eleonora D. Ilieva、Nevena I. Petkova、Rositca D. Nikolova
DOI:10.3390/molecules17054936
日期:——
A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxy-pyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.
Potassium Fluoride Promoted Reaction of 3-Acylsubsti-Tuted 2H-1-Benzopyran-2-Ones with Acid Anhydrides. An Improved Method for the Synthesis of 4-(2-Oxoalkyl)-2H-Chroman-2-Ones. Part III<sup>1</sup>
作者:Anka Bojilova、Nestor A. Rodics、Rozitsa Nikolova、Christo Ivanov
DOI:10.1080/00397919208019275
日期:1992.3
Abstract The reaction of 3-acylsubstituted 2H-1-benzo-pyran-2-ones 1, 5 and 11a-c with acid anhydrides in the presence of potassiumfluoride (KF)/molecular sieves 4A gives the 4-(2-oxoalkyl)-2-oxochromans 2, 6 and 12a-c as the main products. Also the 3-carboxylic acid derivatives, such as esters and N,N-dialkylamides, of 2H-1-benzopyran-2-one (11d-g) react with isobutyric acid anhydride in the presence
Abstract The steric and electronic effects of acyl substituents COR (R = Me, i-Pr, Ph and t-Bu) upon conformational and keto—enol equilibria in 3-acyl-3,4-dihydrocoumarins have been studied by 1 H and 13 C NMR spectroscopy. With the increase of the effective size of R, preference for the equatorial position and the keto-form population increases considerably. The 13 C substituent-induced chemical shifts
摘要 1 H 和 13 研究了酰基取代基 COR(R = Me、i-Pr、Ph 和 t-Bu)对 3-酰基-3,4-二氢香豆素的构象和酮-烯醇平衡的空间和电子效应。 C 核磁共振光谱。随着 R 的有效大小的增加,对赤道位置和酮型人口的偏好显着增加。还讨论了 13 C 取代基引起的化学位移。
Reaction of 2a,8b-Dihydrobenzo[<i>b</i>]cyclobute[<i>d</i>]pyran-3-ones with Dimethylsulfoxonium Methylide
Using dimethylsulfoxonium methylide as the methylene transfer reagent, 2a,8b-dihydrobenzo[b]cyclobute[d]pyran-3-ones were converted into 2,2'-biphenol derivatives as major products and dihydrodibenzofurans as minor products. The reaction mechanism was extrapolated from a deuteration experiment with CD2=S(O)(CD3)2.