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-     

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.     

钯催化下全氟碳负离子的产生及其反应

2-三氟甲基-3-氧杂-八氟己酸烯丙酯或2,5-二(三氟甲基)-3,6-二氧杂-十二氟壬酸烯丙酯可在钯的作用下产生相应的全氟碳负离子. 这些碳负离子能够质子化或者对取代苯甲酰氯发生亲核进攻, 后者为芳基氟烷基酮的合成提供了一条简捷途径. 另一方面,上述含氟酸的甲酯和取代苯甲酰氯在钯的作用下同样能发生反应而生成相应的芳基氟烷基酮.     

一种含三氟甲基和咕吨结构聚酰胺的合成与性能

在浓硫酸和3-巯基丙酸催化下,3'-三氟甲基苯基-2,2,2-三氟苯乙酮(1)和甲苯于40～50℃下缩合反应8 h,制得中间体-1,1-二(4-甲基苯基)-1-(3'-三氟甲基苯基)-2,2,2-三氟甲基乙烷(2),继而在光照和N-溴代丁二酰亚胺促进下,将中间体氧化得到二羧酸-1,1-二(4-羧基苯基)-1-(3'-三...     

柱前衍生化法分离3-羟基丁酸乙酯光学异构体

采用三氟乙酸酐柱前衍生化在β-环糊精毛细管柱(CyclodexB)上分离3-羟基丁酸乙酯光学异构体.考察了衍生化反应条件对3-羟基丁酸乙酯衍生化反应的影响,柱温对3-羟基丁酸乙酯衍生物3-(2,2,2-三氟乙酰氧基)丁酸乙酯光学异构体分离的影响.通过光学异构体分离过程中的热力学参数的计算,探讨光学异构体分离过程的驱动力.实验结果表明,当三氟乙酸酐与3-羟基丁酸乙酯的摩尔比为5:1时,室温下反应5 min,3-羟基丁酸乙酯可定量转化成3-(2,2,2-三氟乙酰氧基)丁酸乙酯;在柱温为62℃时,3-(2,2,2-三氟乙酰氧基)丁酸乙酯光学异构体的分离因子(α)和分离度(R)分别为1.02和1.26.而且,3-(2,2,2-三氟乙酰氧基)丁酸乙酯光学异构体的拆分过程主要是一个焓驱动的过程,且β-环糊精表面与3-(2,2,2-三氟乙酰氧基)丁酸乙酯之间的相互作用在其分离过程中起了重要作用.     

一种含三氟甲基和呫吨结构聚酰胺的合成与性能

在浓硫酸和3-巯基丙酸催化下,3′-三氟甲基苯基-2,2,2-三氟苯乙酮(1)和甲苯于40～50℃下缩合反应8 h,制得中间体-1,1-二(4-甲基苯基)-1-(3′-三氟甲基苯基)-2,2,2-三氟甲基乙烷(2),继而在光照和N-溴代丁二酰亚胺促进下,将中间体氧化得到二羧酸-1,1-二(4-羧基苯基)-1-(3′-三氟甲基苯基)-2,2,2-三氟甲基乙烷(3),二步反应总收率为77.4%.采用Yamazaki体系,3和9,9-二[(4-氨基苯氧基)苯基]呫吨进行溶液亲核缩聚反应,制得了一种高分子量的(数均分子量为43000,分子量分布为1.8)新型含三氟甲基和呫吨结构的聚酰胺.该聚酰胺为非晶态结构并具有良好的透光率(λcutoff=330 nm),其玻璃化转变温度(Tg)为242℃,在氮气气氛中5%的热失重温度(Td5)为465℃,800℃时的残炭率为50%.聚合物易溶于N,N-二甲基乙酰胺(DMAc)、N-甲基吡咯烷酮(NMP)、间甲酚、吡啶(Py)和四氢呋喃(THF)等有机溶剂中,并可浇注得到韧性好和透明的薄膜,其拉伸强度为85 MPa,拉伸模量为2.0 GPa,断裂伸长率为10%.同时,该聚合物的体积电阻、表面电阻和介电常数分别为2.85×1015Ωcm,4.23×1014Ω和3.55(100 Hz),呈现了良好的电绝缘性能.     

可见光照射下卤键引发的多氟烷基溴化物与邻二芳基异腈的自由基型插入反应

报道了一种由卤键引发的自由基型双异腈插入反应.多氟烷基溴化物作为卤键的给体,有机碱作为卤键的受体.在可见光照射下,卤键复合物发生单电子转移过程生成多氟烷基自由基,被邻二芳基异腈捕获生成2-多氟烷基化喹喔啉衍生物.该反应在室温条件下进行,产率高,底物适用性广.反应的自由基属性可以通过EPR实验验证.2-多氟烷基化喹喔啉衍生物中3-位氢源可以通过氘代实验确定,实验显示氢源来自于有机碱和溶剂,而且溶剂是最主要的氢源.     

碱引发下全卤代烷之间的卤素交换反应研究

利用碱的亲卤进攻,既可引发一些含溴与含氯全卤代烷之间进行溴-氯交换反应,也可引发单个含溴、氯全卤代烷进行自身的溴-氯交换反应.此卤素交换反应条件温和,为全卤代烷的合成提供了一条新的途径.并对交换反应的机理进行了初步地探讨,认为反应主要是经由碱的亲卤进攻引发产生碳阴离子中间体后,多步碳阴离子与全卤代烷之间的亲卤进攻的机理所进行的,各种交换产物的量是这种多步交换反应达到平衡后的结果.     

溴代二苯酮与丙腈负离子的光诱导加成反应

<正> 芳香卤代物芳环上的卤原子在光诱导或电引发下可通过自由基链式亲核取代反应(S_(RN)|)而被有机负离子所取代。 我们以3-溴苯基-苯基-甲酮为底物,在丙腈碳负离子存在下进行光照,结果芳酮环上的溴原子未发生 S_(RN)|取代,而是在羰基上发生了光诱导加成反应,生成了未见文献报道的新化合物1-苯基-1-(3-溴苯基)-2-氰基丙醇-1(I)     

气相中正丁烯负离子与N_2O反应机理的理论研究

采用二阶微扰理论(MP2)计算方法,在6-31++G(d,p)的基组下,对气相中正丁烯负离子与N2O反应的微观机理进行了较为系统的理论计算研究,并在相同基组下进一步用QCISD方法在MP2优化的几何构型基础上做了单点能校正.计算结果表明,正丁烯负离子有顺式和反式异构体,它们的伯碳和仲碳都可以与N2O反应,前者的反应有α-H抽提、β-H抽提、基于IM11和氧抽提路径.而α-H抽提为主要反应路径,产物是丙烯基重氮甲基负离子(cis-CH3CHCHCN-N-,trans-CH3CHCHCNN-).后者的反应有甲基H抽提、乙烯基H抽提、基于IM12'和氧抽提路径,其中甲基H抽提为主反应路径,产物是丁二烯负离子,相比之下,在仲碳位置上的反应更有利一些.抽提氧的反应路径也是主反应的竞争路径,其产物应该能被检测到.此外,不管是主反应路径还是次反应路径都是强放热过程.     

Rationally functionalized deltahedral zintl ions: synthesis and characterization of [Ge9-ER3]3-, [R3E-Ge9-ER3]2-, and [R3E-Ge9-Ge9-ER3]4- (E=Ge, Sn; R=Me, Ph)

Six new derivatized deltahedral Zintl ions have been synthesized by reactions between the known Zintl ions Ge(9) (n-) with the halides R(3)EX and/or the corresponding anions R(3)E(-) for E=Ge or Sn. This rational approach is based on our previous discovery that these derivatization reactions are based on nucleophilic addition to the clusters. All species were structurally characterized as their salts with potassium countercations sequestered in 2,2,2-crypt or [18]crown-6 ether. The tin-containing anions were characterized also in solutions by (119)Sn NMR spectroscopy. The reaction types for such substitutions and the structures of the new anions are discussed.     

S(RN)1 Reactions of 7-Iodobicyclo[4.1.0]heptane, 1-Iodoadamantane, and Neopentyl Iodide with Carbanions Induced by FeBr(2) in DMSO

There was no reaction of 7-iodobicyclo[4.1.0]heptane (7-iodonorcarane, 1) (exo-endo ratio of ca. 1) with acetophenone enolate ions 2 in DMSO at 25 degrees C; however, with the addition of SmI(2) or FeBr(2) and under the same experimental conditions, the substitution product 3 was obtained in 9% and 72% yields, respectively, with an exo-endo ratio of ca. 16 similar to the product ratio from photostimulated reactions. Thus, it seems that 7-norcaranyl radicals are intermediates of these reactions. With FeBr(2) at 60 degrees C the yield of 3 was as high as 90%. Reactions of 1 with the enolate ion of 2-naphthyl methyl ketone 4 induced by FeBr(2) gave substitution product 5 in 60% yield (96% of it the exo isomer). In competition experiments, 4 was 1.7 times more reactive than 2, and the anion of nitromethane (7) was 6.5 times more reactive than 2 toward 7-norcaranyl radicals. The reactions of 1-iodoadamantane (9) and neopentyl iodide (11) with carbanion 2 induced by FeBr(2) gave the substitution products in 85% and 92% yields, respectively. These observations indicate that all these reactions induced by FeBr(2) occur by the S(RN)1 mechanism.     

New Triheterocyclic Ring System. Synthesis of Functionalized Pyrazolo[3,4‐d]Pyrimido[1,2‐b][1,2,4,5]Tetrazine Derivatives

New functionalized pyrazolo[3,4‐d]pyrimido[1,2‐b][1,2,4,5]tetrazine derivatives 6a‐q were synthesized via reaction of the hydrazonoyl halides 1a‐q with 5‐amino‐1‐phenyl‐6‐thioxo‐pyrazolo[3,4‐d]pyrimidin‐4‐one 2 and its 2‐methylthio derivative 3 . The mechanism and the regioselectivity of the studied reactions have been discussed.     

"One-pot" two-step synthesis of aryl sulfur compounds by photoinduced reactions of thiourea anion with aryl halides

[reaction: see text]. The photoinduced reactions of aryl halides with the thiourea anion afford arene thiolate ions in DMSO. These species without isolation, and by a subsequent aliphatic nucleophilic substitution, S(RN)1 reaction, oxidation, or protonation, yield aryl methyl sulfides, diaryl sulfides, diaryl disulfides, and aryl thiols with good yields (50-80%). This is a simple and convenient approach which involves the use of the commercially available and inexpensive thiourea in a "one-pot" two-step process for the synthesis of aromatic sulfur compounds.     

Rearrangements of the carbanions derived from allyl benzyl thioether

The metalation of allyl benzyl thioether involves the benzylic or the allylic hydrogens. The benzylic carbanion undergoes a rapid[2,3] sigmatropic shift whereas the allylic carbanion gives rise to various rearrangements, among them migration of the allylic unit to the para position with allylic inversion. The temperature dependence of the ratio of products arising from the benzylic carbanion vs those from the allylic carbanion shows that the allylic-to-benzylic carbanion transformation occurs only under special conditions: (a) with slow addition of the base; (b) with thioether in excess relative to the base, and (c) on raising the temperature of the reaction medium from ?78° to ?15°. In the last instance, the proton transfer is intramolecular as shown with labeled thioethers. The extent of the different rearrangements depends on the temperature and solvent. A choice of mechanism cannot be made at this time for the para migration 5→9a. A leaving group effect on the reaction regioselectivity of the carbanion from allyl methyl thioether with benzyl halides has been noticed. The presence of dibenzyl indicates that, in addition to S_N2 reactions, some electron transfer process is occurring.     

Stereochemistry of the Vinylic S(RN)1 Reaction of Triarylvinyl Halides. The Structure of the Intermediate alpha-Arylvinyl Radical

Evidence for the intermediacy of a vinyl radical in the vinylic S(RN)1 reaction (S(RN)1(V)) of 2-anisyl-1,2-diphenylvinyl bromide 2 is obtained. The photostimulated S(RN)1(V) reaction of pinacolone enolate ion with (E)-2 and (Z)-2, which are used as stereoindicators, gives complete loss of the original stereochemistry of the two precursors in the substituted and hydrodehalogenated products; i.e., stereoconvergence is found. It is concluded that in the reaction of 2 a beta-substituted alpha-phenylvinyl radical is a reactive intermediate and that it has either a linear structure or an average linear structure due to a rapidly interconverting E,Z mixture of bent radicals. This conclusion is supported by comparing the stereochemical course of the S(RN)1(V) reaction with those of other reactions of the same precursor, which unambiguously give rise to the same alpha-phenylvinyl radical intermediate by alternative mechanisms. Among the reactions investigated, the hydrodehalogenation of precursor 2 by LAH appears to take place by an ET mechanism.     

Low-temperature dehalogenation of benzyl halides with atomic magnesium in the3P state

Low-temperature reactions of benzyl halides with magnesium in the³P state proceed according to the radical mechanism accompanied by abstraction of the halogen atom by the biradical magnesium atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 147–151, January, 1999.     

Sequential photostimulated reactions of trimethylstannyl anions with aromatic compounds followed by palladium-catalyzed cross-coupling processes

The photostimulated reactions of several mono-, di-, and trichloroarenes and aryltrimethylammonium salts with Me(3)Sn(-) ions in liquid ammonia gave good yields of stannanes by the S(RN)1 mechanism. If the chloroarenes are not soluble in liquid ammonia, diglyme is another solvent to perform these reactions. The stannanes thus obtained can be arylated by further reaction with haloarenes through palladium-catalyzed reactions. If the palladium-catalyzed reaction is performed with a chloroiodoarene as substrate, the stannane reacts faster by the C-I bond via chemoselective cross-coupling reaction to give a chloroarene as product, which can be further arylated by a consecutive S(RN)1-Stille reaction or react with other substrates by another palladium-catalyzed reaction. These sequential reactions can also be performed with substrates with two leaving groups to give products in high yields.     

Derivation of fluorine-containing pyridinedicarboxylates. III Regio-selective anion chemistry at the 2- and 4-position

In contrast of Part II of the series, 4-alkyl-2-(difluoromethyl)-6-(trifluoromethyl)-3,5-pyridinedicarboxylates, 1 , were reacted with various strength bases to effect regio-selective reaction of electrophiles at either the benzylic carbanion of the 4-position, or at the 2-(difluoromethyl)carbanion. Weaker bases up to and including potassium butoxide or lithium bis(trimethylsilylamide) effected reaction of 1 at the 4-position to produce 2 and 3 by Stobbe-type condensations of aldehydes and ketones. In similar manner carbon disulfide, carbon dioxide, alkyl halides, silyl halides, and hexachloroethane produced the highly functionalized derivatives 4-10. In contrast, use of lithium diisopropylamide and like bases selectively effected carbanion formation at the 2-position to form, with the cited electrophiles and others, substitution products 11. The latter were further derived to the highly functional materials, 12-19.     

Tandem amine propargylation-Sonogashira reactions: new three-component coupling leading to functionalized substituted propargylic amines

Three-component coupling reactions of propargyl halides, amines, and organic halides in the presence of palladium-copper catalysis produced efficiently highly functionalized propargylic amines in good to excellent yields at room temperature. Extension to the synthesis of 2-(dialkylaminomethyl)benzo[b]furan or indole derivatives is described.