环丙烷基三甲基硅醚类化合物的脱硅基及酯化反应的研究

环丙烷基硅醚在卤化锌的作用下能够与硅胶反庆生成环丙基醇。研究了环丙烷基硅醚在卤化锌作用下与酰氯发生的酯化反应,发现在配位性较弱的溶剂二氯甲烷中,可得到比在乙醚中更高的产率。此外,采用一锅煮的方法,从烯醇硅醚出发,经过环丙化反应、酯化反应,以较好的产率合成了环丙基酯。     

非呐酮的烯醇三甲基硅醚在紫外光照下的氟烷基化反应

本文报导了卤代氟烷与酮的烯醇硅醚的反应. 用3,3-二甲基-2-丁酮的烯醇三甲硅醚与等摩尔的1,1,1-三氟-2,2,2-三溴乙烷及催化量的过氧化月桂酰进行紫外光照, 得到二个馏份化合物: 第一馏份为Me3SiBr, 第二馏份含三个化合物, 分别是2,2-二甲基-5,5-二溴6,6,6-三氟-3-己酮, 1,1,1-三氟-2-溴-5,5-二甲基-2-烯-4-己酮和3,3-二甲基-2-丁酮. 上述化合物与NaHCO3或NaOH水溶液反应生成α,β-烯酮(Cl(CF2)n-1CF=CHCOCMe3), 得率好.     

炔丙醇与烯醇硅醚的直接亲核取代反应

报道了一种在对甲苯磺酸催化下炔丙醇和烯醇硅醚的直接亲核取代反应,并有效合成γ-炔基酮类化合物的新方法.该反应在敞口环境下使用未经干燥处理的溶剂即可获得良好的产率.     

N—乙酰乙酰基吡咯及其烯醇硅醚的合成和结构研究

N-乙酰乙酰基吡咯为有机合成上有用的起始原料和中间体。例如,可能作为合成Carbapenam类β-内酰胺化合物的原料。1977年,Wang Nam-Chiang和And-     

具有共轭体系的酮类烯醇硅醚与全氟碘代烷的反应

最近,我们报道了应用连二亚硫酸钠的引发,通过全氟碘代烷与醛类,酮类烯醇硅醚的反应,合成α-全氟烷基羰基类化合物的方法。利用该方法,还可以用“一锅法”合成含     

烯醇硅醚对[60]富勒烯的亲核加成反应

在空气气氛和非极性溶剂(甲苯)中1-(4'-甲氧基苯基)-1-三甲基硅氧基乙烯与[60]富勒烯反应得到了非预计的环丙基骈[60]富勒烯衍生物(5).在无氧和极性非质子性溶剂(THF)中进行上述反应,得到了1,2-取代[60]富勒烯亲核加成产物(3)。对反应的机理作了合理的阐述。     

具有共轭体系的酮类烯醇硅醚与全氟碘代烷的反应

应用连二亚硫酸钠的引发，通过全氟碘代烷与醛类，酮类烯醇硅醚的反应，合成α－全氟烷基羰基类化合物的方法。利用该方法，还可以用“一锅法”合成含氟β－二酮类化合物。本文报道了在类似的反应条件下，与苯环或双键共轭的烯醇硅醚和全氟碘代反应的结果。     

片呐酮的烯醇三甲基硅醚在紫外光照下的氟烷基化反应

酮的烯醇硅醚的富电子碳碳双键易被亲电子基团进攻,生成取代酮类化合物。例如,在TiCl_4等Lewis酸的存在下,卤代烷与酮的烯醇三甲硅醚反应生成2-烷基取代酮。迄今为止,还没有卤代氟烷与酮的烯醇非醚反应研究的报道。我们将3,3-二甲基-2-丁酮的烯醇三甲硅醚与等摩尔的1,1,1-三氟-2,2,2-三溴乙烷及催化量的过氧化月桂酰进行光照3h后,б_F-10 ppm处出现一新峰,与CF_3CBr_3(2)的δ_F0 ppm处峰的面积比为2:3。继续光照,δ_F-     

一个制备手性烯醇硅醚的新方法

本文合成了8个手性烯醇硅醚, 其中5个为新化合物, 其结构为IR, 1HNMR和MS所证实。     

Catalytic asymmetric Simmons-Smith cyclopropanation of unfunctionalized olefins

This paper describes a catalytic asymmetric cyclopropanation system for unfunctionalized olefins using readily available dipeptide N-Boc-l-Val-l-Pro-OMe (1) as ligand.     

One-step cyclopropanation of alkynes with diiodomethane and triethylaluminum

Cyclopropanation of mono- and dialkyl-substituted alkynes under the action of CH₂I₂ and Et₃Al afforded the corresponding 1-alkyl- and 1,2-dialkyl-substituted 1,2-diethylcyclopropanes in 65—80% yields.     

Pathways of Pd-catalyzed cyclopropanation of tetrahydroindene with diazomethane

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New insights on the mechanism of the transition-metal stereoselective olefin cyclopropanation

We have carried out a theoretical analysis of the intermolecular cyclopropanation of propargylic esters with alkenes. DFT calculations allow us to propose a reaction mechanism, and provide explanations for the reasons behind the difference between the inter- and intramolecular versions of this process. The results strongly suggest that the entropic effects could modulate the operative mechanism and account for the mechanistic discrepancy. The calculated model also justifies the experimental stereoselectivity on the basis of intra- and intermolecular interactions. In addition, we have taken into account other transformations of propargylic carboxylates catalyzed by late transition metals, and the results rationalize the accumulated experimental observations.     

Cyclopropane-annelated azaoligoheterocycles by Ti-mediated intramolecular reductive cyclopropanation of cyclic amino Acid amides

Starting from pyrrole- and indole-2-carboxylic acids 5 a and 5 b, the tri- and tetracyclic N,N-dibenzylcyclopropylamines 7 a and 7 b have been synthesized in 52 and 33 % overall yield, respectively. The synthesis of the enantiopure tetracyclic diamine 10 has been achieved applying the established set of reactions to N-tert-butoxycarbonylindoline-2-carboxylic acid (8) in 46 % overall yield. The amide 15 could not be prepared in the same way starting from the N-tert-butoxycarbonylproline 11. In fact, in the allylation step the stereogenic center was deprotonated and the doubly alkylated amide 13 was formed. However, the desired intermediate 15 could be obtained from L-proline in 49 % yield performing first the N-allylation step, then the introduction of the amide function. From 15, the cyclopropane-annelated pyrrolizidine 16 was obtained in 70 % yield as a mixture of (1aS,6aS,6bR)-16 and (1aR,6aS,6bS)-16 diastereoisomers in a ratio of 1:2.9.     

Asymmetric cyclopropanation reactions catalyzed by carbohydrate-based crown ethers

Optically active cyclopropane derivatives were prepared by a novel, simple and green approach in high enantioselectivities using monosaccharide-based chiral crown ethers as phase transfer catalysts. The crown ethers having d-glucopyranoside, d-mannopyranoside and d-altropyranoside units proved to be efficient catalyst in a few asymmetric phase transfer cyclopropanation reactions. The Michael-initiated ring closure (MIRC) reactions of diethyl bromomalonate with chalcones took place with complete diastereoselectivity and up to 99% ee. Using benzylidenemalononitrile, 2-arylidenemalononitriles, 2-benzylidene-1,3-indandione, substituted 2-benzylidene-1,3-indandiones, 2-arylidene-1,3-indandiones and 2-benzylidene-1,3-diphenyl-1,3-propanediones enantioselectivities up to 92%, 99%, 54% 93%, 89% and 72%, respectively, were achieved, in the presence of chiral lariat ethers derived from different monosaccharides. The absolute configuration of a cyclopropane diester product was determined by a combined CD spectroscopic and theoretical study.     

Asymmetric intermolecular cyclopropanation of alkenes by diazoketones catalyzed by Halterman iron porphyrins

The asymmetric addition of diazoacetophenone to styrene derivatives to give optically active cyclopropyl ketones (ee up to 80%) was carried out using chiral iron porphyrins as homogeneous catalysts. Intermolecular N-H functionalization of anilines by means of carbenoid-induced N-H insertion was also possible but without enantioselectivity.