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31.
The direct ketohydroxylation of a variety of 1-aryl-1-alkenes with H2O2, catalyzed by the inexpensive 12-tungstophosphoric acid/cetylpyridinium chloride system under very mild conditions, was achieved. Various acyloins were obtained in good yields and high regioselectivies. 相似文献
32.
半素环的几个交换性条件 总被引:7,自引:0,他引:7
一个半素环 R是交换环当且仅当 R满足下列条件之一 :( ) (xmy) n+xmy∈ Z(R) ,对任意的 x ,y∈ R。( ) (xmy) n- yxm∈ Z(R) ,对任意的 x,y∈ R。( ) (xmy) n+yxm∈ Z(R) ,对任意的 x,y∈ R。其中 m,n是固定的正整数且 n >1 相似文献
33.
关于高阶线性微分方程亚纯解的增长率 总被引:32,自引:0,他引:32
本文研究了二种类型的高阶线性齐次亚纯函数系数微分方程的亚纯解的增长性,当存在某个系数对方程的解的性质起主要支配作用时,我们对方程的亚纯解的增长率得到了精确的估计。 相似文献
34.
The title compound has been synthesized and resolved previously by T. M. Kubiak. In our searching of new potent agonists of LH-RH(luteinizing hormone releasing hormone), α-N-t-butyloxycarbonyl-β-3-quinolyl)-D-α-alanine and its L-isomer were synthesized. The unprotected.optically active amino acids were obtained by enzymatic hydrolysis of the title compounds, followed by hydrolysis in 6 mol/L hydrochloric acid. The title compound was synthesized initially with 3-quinolinecar- 相似文献
35.
36.
Zongxuan Shen 《Tetrahedron letters》2005,46(50):8785-8788
The aldol-type addition of acetone towards (un)substituted benzoyl, heteroarylcarbonyl or α,β-unsaturated acyl cyanides was efficiently catalyzed by l-proline (30 mol %) to give 2-hydroxy-4-oxo-2-substituted pentanenitriles. Upon the treatment with sodium hydroxide, the adducts transformed to 1,3-diketones in good-to-excellent yield, furnishing an efficient and convenient method for the regioselective synthesis of 1,3-diketones. 相似文献
37.
Ultra-deep desulfurization of diesel: oxidation with a recoverable catalyst assembled in emulsion 总被引:8,自引:0,他引:8
Li C Jiang Z Gao J Yang Y Wang S Tian F Sun F Sun X Ying P Han C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2277-2280
A [(C(18)H(37))(2)N(+)(CH(3))(2)](3)[PW(12)O(40)] catalyst, assembled in an emulsion in diesel, can selectively oxidize the sulfur-containing molecules present in diesel into their corresponding sulfones by using H(2)O(2) as the oxidant under mild conditions. The sulfones can be readily separated from the diesel using an extractant, and the sulfur level of the desulfurized diesel can be lowered from about 500 ppm to 0.1 ppm without changing the properties of the diesel. The catalyst demonstrates high performance (>/=96 % efficiency of H(2)O(2), is easily recycled, and approximately 100 % selectivity to sulfones). Metastable emulsion droplets (water in oil) act like a homogeneous catalyst and are formed when the catalyst (as the surfactant) and H(2)O(2) (30 %) are mixed in the diesel. However, the catalyst can be separated from the diesel after demulsification. 相似文献
38.
CHEN Zongxuan 《数学年刊B辑(英文版)》2003,24(4):501-508
The author investigates the hyper order of Solutions of the higher order linear equation, and improves the results of M. Ozawa[15], G. Gundersen[6] and J. K. Langley[12]. 相似文献
39.
考虑了差分多项式f(z)n(f(z)m-1)dΠj=1f(z+cj)vj-α(z)的零点问题,其中f(z)是有穷级的超越整函数.cj(cj≠0,j=1,…,d)是互相判别的常数,n,m,d,vj(j=1,…,d)∈N+,α(z)是f(z)的小函数.还讨论了差分多项式的唯一性问题. 相似文献
40.
我们定义了左、右不变拟了环和完全亚直既约拟环,给出了拟环为拟除环的几个条件.这些结果可以直接推广到结合环. 相似文献