Synthesis and rearrangement of dispiro[2.0.3.4]-, dispiro-[3.0.3.3]- and dispiro[2.1.3.3]undecanes - preferred C4-C5 over C3-C4 and C4-C3 over C5-C6 rearrangements
10–12 have been synthesized and rearranged by treatment with acids. With 10, an initial C3-C4 ringenlargement leads to [3.3.3]propellane 21, with 11, an initial C4-C3 ring contraction leads to pentalene 37, and with 12, an initial C4-C5 ringenlargement leads to 42, 43, 44 or 45, depending on the reagent used. The structure of 43 has been determined by crystal structure analysis of the 3,5-dinitrobenzoate
Synthesis and rearrangement of functionalized dispiro[2.1.3.3]Undecanes - preferred C4C5 over C3C4 ring enlargements
作者:Lutz Fitjer、Marita Majewski、Andreas Kanschik、Ernst Egert、George M Sheldrick
DOI:10.1016/s0040-4039(00)84860-1
日期:1986.1
The functionalized dispiro[2.1.3.3]undecanes and undergo cascade rearrangements to yield the bi- and tricyclic systems , , and , respectively. The rearrangements proceed via an initial enlargement of the four-membered ring.
Reactivite des derives de cyclopropylidene-3 propyle-I
作者:M. Bertrand、G. Leandri、A. Meou
DOI:10.1016/s0040-4020(01)98934-3
日期:1981.1
β-cyclopropylidenic alcohols has been synthesized through the following sequence: (i) Wittig condensation between cyclopropylidenetriphenylphosphorane with appropriate monoprotected 1,3-dicarbonyl compounds; (ii) smooth hydrolysis of acetals (after a necessary transacetalization step) and ketals thus formed; (iii) LAH reduction of aldehydes and ketones (yielding primary and secondary alcohols respectively)
Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewisacid properties that solubilizes
亚甲基环丙烷(MCP)与第一和第二族金属卤化物和卤化铵在液体SO 2中进行开环反应,得到均烯丙基卤化物,它们是有机合成中的通用试剂。所开发的反应条件与酸不稳定的底物如N -Boc保护的化合物相容。液体SO 2是具有路易斯酸性质的极性反应介质,可溶解无机盐。通过对照实验证明了SO 2的独特性质:1)在常规溶剂中与上述盐进行反应后,在催化量的H 3 PO 4(相似的pK)存在下也未观察到MCP开环a等于H 2 SO 3),或不存在H 3 PO 4;2)SO 2在THF中的溶液表现出与液体SO 2相似的性质。
Selective Wittig Reactions for the Synthesis of Variously Substituted 2-Vinylindoles
作者:Manfred Eitel、Ulf Pindur
DOI:10.1055/s-1989-27253
日期:——
Three selective variants of the Wittig reaction for the syntheses of 2-vinylindoles are described. The reactions are relatively easy to perform, exhibit E-selectivity, and are characterized by a good flexibility with regard to the functional groups present in the vinyl moiety.