New chemical access for pyran core embedded derivatives from bisalkenylated 1,3-diketones and 1,3-diketoesters via tandem C-dealkenylation and cyclization
摘要:
New chemical access has been developed for the synthesis of pyran core embedded derivatives from 1,3-diketones and 1,3-diketoesters, in which the active methylene group of 1,3-diketone or 1,3-diketoester was alkenylated with three equivalents of alkenyl bromides in presence NaH to give bisalkenyl 1,3-diketones or 1,3-diketoesters and the resultant bisalkenyl 1,3-diketones or 1,3-diketoesters were reacted with AlCl3 at room temperature to furnish pyran core embedded derivatives in good to excellent yields. (C) 2010 Elsevier Ltd. All rights reserved.
Brønstedacidscatalyze the addition of enolizable β-diketones, β-ketoesters, and vinylogous amides to α,β-unsaturated aldehydes to lead to substituted chromenones, pyranones, and tetrahydroquinolinones in good yields under mild reaction conditions via a formal [3 + 3] cycloaddition.
Isoprene: A Promising Coupling Partner in C–H Functionalizations
作者:Qing-An Chen、Wei-Song Zhang、Yan-Cheng Hu
DOI:10.1055/s-0040-1707172
日期:2020.10
basic industrial feedstock isoprene is an ideal alternative precursor. However, given that electronically unbiased isoprene might undergo six possible addition modes in the coupling reactions, it is difficult to control the selectivity. This article summarizes the strategies we have developed to achieve regioselective C–H functionalizations of isoprene under transition-metal and acid catalysis. 1 Introduction
I2–PPh3 mediated spiroannulation of unsaturated β-dicarbonyl compounds. The first synthesis of (±)-negundoin A
作者:Rubén Tapia、Ma José Cano、Hanane Bouanou、Esteban Alvarez、Ramón Alvarez-Manzaneda、Rachid Chahboun、Enrique Alvarez-Manzaneda
DOI:10.1039/c3cc45921g
日期:——
An efficient and stereoselective spiroannulation of unsaturated enols is reported. Unsaturated beta-dicarbonyl compounds undergo cyclization by reaction with catalytic I2-PPh3, affording the corresponding spiro enol ether derivatives, with complete regio- and stereoselectivity, under mild conditions. Utilizing this new methodology, the first total synthesis of the anti-inflammatory diterpene negundoin
Abstract The chemoselective C- and O-prenylation of cyclic1,3-diketones was achieved by tuning the prenyl source and catalyst. In the presence of the solid acid Nafion, the coupling of 1,3-cyclohexanediones with isoprene gave C-prenylated 5-chromenones. Alternatively, using prenol as the substrate with the Lewis acid AlCl3 as the catalyst resulted in the exclusive O-prenylation of 1,3-cyclohexanediones