排序方式: 共有97条查询结果,搜索用时 15 毫秒
1.
Ralf Otte Roland Fröhlich Shuichi Nakamura Takeshi Toru Dieter Hoppe 《Tetrahedron letters》2007,48(49):8636-8642
The enantio- and diastereoselective synthesis of allenyl aryl sulfides by asymmetric lithiation of 2-alkynyl (2-hetero)aryl sulfides is described. A dynamic thermodynamic resolution by selective crystallization of the intermediate lithium complexes derived from deprotonation, applying a bis(oxazoline) ligand, was achieved to give enantioselectivities up to 85% ee. Subsequent stereospecific nickel-catalyzed cross-coupling reactions with arylzinc reagents established a versatile access to threefold carbon-substituted allenes. 相似文献
2.
Alkyl substituted chromium Fischer carbene complexes react with 1,1-diphenylallene in the presence of rhodium(I) catalysts (10 mol%) to yield highly substituted dienyl indenone derivatives. In this process a catalytic chromium(0)-rhodium(I) exchange occurs, four new C-C bonds are created, and four-components (two allenes, the carbene ligand and one CO ligand) are joined in a chemo- and regioselective manner. 相似文献
3.
An efficient method for the synthesis of valuable N-, O-, and Si-containing 1Z,5Z-diene compounds was developed. The method comprises Cp2TiCl2-catalyzed homo- and cross-cyclomagnesiation of 1,2-dienes by Grignard reagents (RMgR′) to give 2,5-dialkylidenemagnesacyclopentanes in up to 96% yield. This approach was successfully used in the synthesis of 5Z,9Z-dienoic acids, precursors of acetogenins and insect pheromones. 相似文献
4.
An efficient gold-catalyzed procedure for the preparation of 2-vinylimidazolidinones has been developed. The starting materials for the synthesis of these compounds are α-amino allenamides which undergo heterocyclization by means of nucleophilic attack of the amino group on the inside double bond of the 1,2-diene moiety. This is the first example of a gold-catalyzed cyclization on allene substrates bearing an amido group which, however, resulted inactive. 相似文献
5.
Amelie Heuer-JungemannRoss G. McLaren Maximillian S. HadfieldAi-Lan Lee 《Tetrahedron》2011,67(9):1609-1616
Gold(I)-catalysed intermolecular iodoalkoxylation of allenes occurs in a regioselective and stereoselective manner to produce versatile iodo-tert-allyllic ether products. The products can be further elaborated through cross-couplings to yield highly substituted tert-allylic ethers. 相似文献
6.
A series of nitrogen‐tethered allenynes (‘5‐aza‐1,2‐dien‐7‐ynes’) 1 were transformed to the corresponding 3‐acyl‐4‐alkenylpyrrolidines 3 when treated with a catalytic amount of PtCl2 in MeOH at 70°. Initial Pt‐promoted cyclization forms a nonclassical carbocationic intermediate. In contrast to the cycloisomerization in toluene, which produced the bicyclic cyclobutenes 2 , the intermediate is intercepted by addition of an oxygen nucleophile to achieve the formal hydrative cyclization. 相似文献
7.
Samuel Braverman Tatiana Pechenick Hugo E. Gottlieb Milon Sprecher 《Tetrahedron letters》2004,45(44):8235-8238
The first successful preparation of propargylic and allylic chloroalkoxy disulfides in high yields is reported. Facile 1,4-electrophilic addition of these to 2,3-dimethyl-1,3-butadiene, followed by [2,3]-sigmatropic rearrangements affords mixed allyl allenic and bis-allylic thiosulfinates, respectively. Due to their similarity to allicin, the latter are of potential biological interest. 相似文献
8.
Regio- and stereoselective sulfonylation of allenes under Cu catalysis is described. Allenyl sp carbons exclusively react with TsCN to give the corresponding alkenyl sulfones. The reaction is initiated by addition of tosyl radical to form benzyl radical intermediates, which determines the reaction pathway. The structure of the products is highly dependent on the substituents on allenes. 相似文献
9.
A nickel-catalyzed [2 + 2] cycloaddition of bisallenes has been described. Simple bisallenes are employed for the formation of “head to head” cycloadducts in the presence of Ni(0) with xantphos. The dienyl moiety in a product were applicable for various [4 + 2] cycloaddition reactions. Allene-allenamides under Ni-xantphos system gave the tricyclic compounds through sequential [2 + 2]–[4 + 2] cycloaddition reaction in highly stereoselective manner. 相似文献
10.
Xin-Yu Gong Yang Chen Li-Heng Ruan Yu-Ke Liu Jing Sun 《Journal of Saudi Chemical Society》2019,23(8):1137-1143
The regioselective hydroamination of diphenylphosphorylallenes has been developed using secondary amines as the amination reagents. This reaction protocol could be realized under ligand and transition metal-free conditions at room temperature and is tolerated to a diverse range of diphenylphosphorylallenes and amine substrates, affording a series of β-aminophosphine oxides in good yields after the reduction of the enamine intermediates. 相似文献