Unsaturated malonyl esters underwent Pd-catalyzed intramolecular allylic alkylation to give 4-vinyl-substituted γ-lactones. In contrast to the previously studied cyclization of malonamides, this reaction could only be achieved with a substrate incorporating a judiciously positioned silicon moiety, which directs the ionization toward the desired η 3 -allyl-palladium complex. The resulting 4-[dimeth
engaged into Hiyama couplings with various iodoarenes, to give the corresponding 4-(α-styryl)-γ-lactones. The use of a specifically substituted iodoarene generated an advanced tetracyclic lactone intermediate incorporating rings A−D of lignans belonging to the podophyllotoxin family. Subsequent electrophilic aromatic substitution with a variety of electron-rich arenes afforded the target picropodophyllin
through an organophosphorus-catalyzed borylative ring-opening/allylation of vinylcyclopropanes providing δ-hydroxy estersstereoselectively. The δ-hydroxy esters were lactonized to obtain densely substituted δ-valerolactones. The present methodology exhibited enhanced functional group tolerance compared to the existing metal-mediated methods. A plausible mechanism for borylative ring-opening reaction
我们通过有机磷催化的乙烯基环丙烷的硼基化开环/烯丙基化立体选择性地提供 δ-羟基酯,报告了一种操作简单的 δ-戊内酯途径。δ-羟基酯被内酯化以获得密集取代的δ-戊内酯。与现有的金属介导方法相比,本方法表现出增强的官能团耐受性。已经提出了一种可能的硼酸化开环反应机制。31 P NMR 研究表明磷鎓两性离子种类的参与。证明了中间体硼酸烯丙酯的合成效用。
Synthesis of methyl 2-oxo-5-vinyl-2,5-tetrahydrofuran-3-carboxylate
作者:Maximilian A. Silvestri、Chang He、Anita Khoram、Salvatore D. Lepore
DOI:10.1016/j.tetlet.2005.12.114
日期:2006.3
A synthesis of methyl 2-oxo-5-vinyl-tetrahydrofuran-3-carboxylate involving five synthetic steps from commercially available 3,4-dihydroxybutene is reported. (c) 2006 Elsevier Ltd. All rights reserved.
TfOH-Catalyzed Formal [3 + 2] Cycloaddition of Cyclopropane 1,1-Diesters with Nitriles
作者:Bo Cui、Jun Ren、Zhongwen Wang
DOI:10.1021/jo402383a
日期:2014.1.17
A triflic acid-catalyzed formal [3 + 2] cycloaddition of cyclopropane 1,1-diesters with nitriles was developed. This reaction was expeditious, and the scope of the substituents in both cyclopropanes and nitriles was broad. This supplies an efficient and practical method for the synthesis of 1-pyrrolines.