Synthesis of δ-lactones from 2-alkynyl epoxides and 4-alkynyl-1,3-dioxolan-2-ones by palladium catalysed carbonylation and conjugate nucleophilic addition
作者:Julian G. Knight、Simon W. Ainge、Carl A. Baxter、Timothy P. Eastman、Simon J. Harwood
DOI:10.1039/b006927m
日期:——
Palladium catalysed carbonylation of both 4-alkynyl-1,3-dioxolan-2-ones and alkynyl epoxides occurs under mild conditions to give methyl 5-hydroxy-2,3-dienoates which are converted to γ,δ-unsaturated δ-lactones by tandem conjugate additionâcyclisation with lithium dimethylcuprate or to methyl (E)-5-hydroxypent-3-enoates by stereoselective reduction with sodium borohydride.
The reaction of propargylic oxiranes with platinum catalyst in aqueous media is described. Furans having a variety of substituents were conveniently synthesized with high efficiency.
描述了炔丙基环氧乙烷与铂催化剂在水性介质中的反应。具有各种取代基的呋喃可方便地以高效率合成。
Synthesis of amino allenes via reaction of α-aminoalkylcuprates with propargyl substrates
作者:R.Karl Dieter、Lois E Nice
DOI:10.1016/s0040-4039(99)00778-9
日期:1999.6
α-Aminoalkylcuprates prepared from carbamates via sequential deprotonation and treatment with CuCN·2LiCl react with propargyl bromides, mesylates, tosylates, acetates, and epoxides to afford amino allenesvia a SN2′ substitution process. Propargyl bromides and sulfonates give good yields of amino allenes while the acetates afford low yields. Substrates undergo regiospecific SN2′ substitution and the
由氨基甲酸酯经顺序去质子化制得的α-氨基烷基铜酸酯,并用CuCN·2LiCl处理,与炔丙基溴,甲磺酸酯,甲苯磺酸酯,乙酸酯和环氧化物反应,经S N 2'取代过程制得氨基丙二烯。炔丙基溴和磺酸盐提供了良好的氨基丙二烯收率,而乙酸酯提供了低收率。底物进行区域特异性S N 2'取代,使用Sc(OTf)3可提高炔丙基环氧化物的氨基丙二烯收率。Boc保护的α-氨基丙二烯可以环化为恶唑烷酮或脱保护得到游离胺。
Silver(I)-Catalyzed Cascade: Direct Access to Furans from Alkynyloxiranes
作者:Aurélien Blanc、Katharina Tenbrink、Jean-Marc Weibel、Patrick Pale
DOI:10.1021/jo900483m
日期:2009.6.5
Functionalized furans are conveniently formed by a new silver(I)-catalyzed reaction of alk-1-ynyl oxiranes in the presence of p-toluenesulfonic acid and methanol. Evidence supported a cascade mechanism.
Mechanistic Studies and Improvement of Coinage Metal-Catalyzed Transformation of Alkynyloxiranes to Furans: An Alcohol Addition−Cyclization−Elimination Cascade
作者:Aurélien Blanc、Katharina Tenbrink、Jean-Marc Weibel、Patrick Pale
DOI:10.1021/jo9008172
日期:2009.8.7
In the presence of alcohol Ag or Au salts or complexes catalyze the conversion of alkynyloxiranes to substituted furans. Both-catalysts are effective, and a large furan diversity can be obtained in high yield with one or the other catalyst. Mechanistic studies revealed that a cascade pathway and not the sometimes reported direct intra molecular nucleophilic addition of oxirane oxygen atom to intermediate acetylene-metal pi-complex occurs. Under the defined conditions, the intermediate formation of epoxide opening products has been identified. Depending on the catalyst, one or both of the latter cyclized to dihydrofurans, and further elimination of the alcohol led to the corresponding furans. These results highlight the duality between oxophilicity and alkynophilicity of Ag or Au salts.