含有五元碳环的二吡咯中间体很容易从环戊[ b ]吡咯制备,该单元代表在富含机油的沉积物(如油页岩和石油)中发现的DPEP型地卟啉的南半部分。当在温和的酸性条件下与二吡咯甲烷甲醛反应时,具有六元,七元或八元碳环的相关二吡咯显示出b- ene。末端酯基脱保护后,用TFA-CH(OMe)3环化得到一系列的脱氧叶绿体铁卟啉(DPEP)环同系物。在b由五元环二吡咯生成的β-二烯被证明是相当不稳定的,必须不经纯化直接使用。环化产生DPEP并被埃菲卟啉副产物污染,但可以通过快速色谱法将其分离为镍(II)衍生物。与先前报道的方法相比,该方法可产生更高的DPEP产量。另外,该方法可以扩展到相关的卟啉的合成,并且通过这种方法合成了由细菌叶绿素d衍生的一系列五种分子化石。
New Oxidation of β-Hydroxy α-Methyl Ketones: A Convenient Synthesis of 3-Methylalkane-2,4-diones
摘要:
The synthesis of 3-methylalkane-2,4-diones, which are intense strawlike and fruit-flavored compounds, has been performed by the aldol condensation of n-alkanal (C2-C7) and methyl ethyl ketone to give 4-hydroxy-3-methyl-2-alkanones in 31-72% yield, followed by oxidation using sodium hypochlorite in the presence of 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-N-oxide in 60-86% yield.
Sulfidkontraktion<i>via</i>alkylative Kupplung: Eine methode zur darstellung von β-dicarbonylderivaten. Über synthetische methoden, 1. Mitteilung
作者:M. Roth、P. Dubs、E. Götschi、A. Eschenmoser
DOI:10.1002/hlca.19710540229
日期:——
The experiments described in reaction schemes 1–12 indicate that sulfide contraction via alkylative coupling (see scheme p. 729) is a potentially general method for the synthesis of secondary vinylogous amides and enolizable β-dicarbonyl compounds.
The Universal Mobile Telecommunications System (UMTS) is one of the new 'third generation' mobile cellular communication systems. UMTS builds on the success of the 'second generation' GSM system. One of the factors in the success of GSM has been its security features. New services introduced in UMTS require new security features to protect them. In addition, certain real and perceived shortcomings of GSM security need to be addressed in UMTS. This paper surveys the major security features that are included in the first releases of the UMTS standards.
Chiral Primary Amine Catalyzed
<i>α</i>
‐Arylation of Simple Ketones via Asymmetric Retro‐Claisen Cleavage
作者:Yanfang Han、Mingying Shi、Xueling Mi、Sanzhong Luo
DOI:10.1002/chem.202202584
日期:2022.12.20
C−C cleavage to arylation. Enantioselective α-arylation of simple aliphatic ketones has been achieved via chiral primary amine catalyzed asymmetric retro-Claisen cleavage involving β-diketones and para-quinone monoimines that facilitates the construction of α-aryl tertiary carbon stereocenters in good yields and high enantioselectivities.
Polyamide acid composition for preparing polyimide and process for preparing polyimide from the same
申请人:KANEGAFUCHI KAGAKU KOGYO KABUSHIKI KAISHA
公开号:EP0083690A1
公开(公告)日:1983-07-20
A polyamide acid composition for preparing a polyimide which can extend the pot life of the composition comprising a solution of a polyamide acid in an organic solvent, the polyamide acid being a precursor of the polyimide, a dehydrating agent, a catalyst and a pot life extending agent which can lower a rate of conversion of the polyamide acid to the plyimide, and the process for preparing the polyimide from said polyamide acid composition. According to the present invention the pot life can be extremely extended to give the composition an enough flowability for a long time without reducing the excellent properties such as a heat resistance and an electric insulation of the obtained polyimide.
Method of preparing a polyamide acid composition for preparing polyimide
申请人:KANEGAFUCHI KAGAKU KOGYO KABUSHIKI KAISHA
公开号:EP0114059A2
公开(公告)日:1984-07-25
A polyamide acid composition for preparing a polyimide which is improved in the stability in a form of solution and can extend the pot life of the composition comprising a solution of a polyamide acid in an organic solvent, the polyamide acid being a precursor of the polyimide, and an N-substituted heterocyclic compound as a chemical treating agent which can lower a rate of conversion of the polyamide acid to the polyimide. The pot life can be extremely extended to give the composition an enough flowability for a long time without reducing the excellent properties such as a heat resistance of the obtained polyimide.