四异丙氧基钛对苯偶姻体系的氧化反应

Ti(OPr^i)4作为氧化剂直接氧化有机物尚属首例, ti(OPr^i)4很容易将苯偶姻氧化生成苯偶酰。室温下, 以THF作溶剂, 反应仅需10min。同样, Ti(OPr^i)4也能将氯、甲基和甲氧基取代的苯偶姻以及糠偶姻(Furoin)氧化生成相应的二酮。实验结果表明:Ti(OPr^i)4与苯偶姻体系的反应, 条件温和, 产率很高, 是一条实用、而有效的由苯偶姻制备苯偶酰的途径。     

四异而氧基钛对苯偶姻体系的氧化反应

在水溶液中,很多试剂,如浓硝酸,Cu~(++)/Py,Bi_2O_3/H~+,Fe(CN)_6~(3-)/OH~-等可将苯偶姻(Benzoin)氧化生成苯偶酰(Benzil),而在有机介质且中性条件下反应的例子不多。Ho曾报道,Ph_3P·Br_2在无水乙腈中能氧化苯偶姻制得苯偶酰,产率75～98％。Swern还使用过Me_2SO/(COCl)_2/CH_2Cl_2,产率64～95％。     

盐酸三甲胺三氧化铬／硅胶载体试剂的制备及其对苯偶姻体系的氧化

报道了盐酸三甲胺三氧化锆／硅胶载体试剂的制备方法及其对苯偶姻的氧化反应。该试剂制备简单，用于地苯偶姻的氧化，高收率地得到相应的苯偶酰在化合物，并且反应条件温和，产物易分离。     

手性胶束的不对称诱导作用不对称苯偶姻缩合反应

胶束体系是模拟酶的简单模型之一。手性胶束对反应有手性诱导作用。在表面活性剂(1R，2S)-(-)-N-十二烷基-N-甲基麻黄素溴化物和(1R，2S)-(-)-N-十六烷基-N-甲基麻黄素溴化物形成的胶束体系中进行的苯偶姻缩合反应，生成了光学活性的α-羟基酮。     

氯铬酸三甲铵/氧化铝的制备及其对醇和苯偶姻类化合物的氧化

本文报道了氯铬酸三甲铵/氧化铝的制备方法及其对醇和苯偶姻类化合物的氧化反应。 该试剂制备简单、性质稳定。氧化反应条件温和、操作简单、提纯方便、收率良好。     

N-羟基邻苯二甲酰亚胺/Co(acac)_2催化的α-紫罗兰酮的氧化反应

以分子氧(O_2)为氧化剂,在无溶剂条件下,研究了N-羟基邻苯二甲酰亚胺/乙酰丙酮亚钴(Ⅱ)体系对α-紫罗兰酮的催化氧化反应,分析了氧化产物,主要得到α-紫罗兰酮的烯丙位氧化产物5-氧代-α-紫罗兰酮,同时生成少量环氧α-紫罗兰酮及重排产物4-氧代-β-紫罗兰酮和环氧β-紫罗兰酮,提出了可能的反应机理,化合物的结构经IR、~1H NMR、MS和EA等测试技术得以表征;为了提高5-氧代-α-紫罗兰酮的选择性和催化氧化反应的转化率,优化了催化氧化反应的工艺条件:当反应温度为70 ℃,氧气压力为1.0 Mpa,N-羟基邻苯二甲酰亚胺和乙酰丙酮亚钴(Ⅱ)用量分别为α-紫罗兰酮的25%和1.0%,反应10 h,5-氧代-α-紫罗兰酮的产率达53.4%,反应转化率达95.0%以上,平行实验表明,实验重复性良好.     

CrO3.CH3NH2.HCl／Al2O3的制备及其对苯偶姻体系的氧化反应

ＣｒＯ３·ＣＨ３ＮＨ２·ＨＣｌ／Ａｌ２Ｏ３的制备及其对苯偶姻体系的氧化反应张贵生＊石启增陈密峰蔡昆（河南师范大学化学系新乡４５３００２）关键词ＣｒＯ３·ＣＨ３ＮＨ２·ＨＣｌ／Ａｌ２Ｏ３，苯偶姻，苯偶酰，氧化１９９６－０８－１８收稿，１９９６－１１－０...     

无外加催化剂条件下2-氨基-3-腈基-4-芳基-7,7-二甲基-5-氧 代-4H-5,6,7,8- 四氢苯并-[b]-吡喃-3-羧酸乙酯的合成

亚苄基氰基乙酸乙酯(1)与5,5-二甲基-1,3-环已二酮在乙二醇中不加任何催化剂于80℃反应2～3h得2-氨基-4-芳基-7,7-二甲基-5-氧化-4H-5,6,7,8-四氢苯并-[b]-吡喃-3-羧酸乙酯(3),产率75%～93%。     

氮羟基邻苯二甲酰亚胺催化的α-紫罗兰酮的氧化反应

以分子氧（O₂）为氧化剂,在无溶剂条件下,研究了N-羟基邻苯二甲酰亚胺/乙酰丙酮亚钴(Ⅱ)体系对α-紫罗兰酮的催化氧化反应,分析了氧化产物,主要得到α-紫罗兰酮的烯丙位氧化产物5-氧代-α-紫罗兰酮,同时生成少量环氧α-紫罗兰酮及重排产物4-氧代-β-紫罗兰酮和环氧β-紫罗兰酮,提出了可能的反应机理,化合物的结构经IR, ¹H NMR, MS和EA等手段得以表征;为了提高5-氧代-α-紫罗兰酮的选择性和催化氧化反应的转化率,优化了催化氧化反应的工艺条件：当反应温度为70 ℃,氧气压力为1.0 MPa,N-羟基邻苯二甲酰亚胺和乙酰丙酮亚钴(Ⅱ)用量分别为α-紫罗兰酮的25%和1.0%,反应10 h,5-氧代-α-紫罗兰酮的产率达53.4%,反应转化率达95.0%以上,平行实验表明,实验重复性良好。     

SBA-15/NiCl2催化超声合成喹喔啉衍生物

以苯偶姻和邻苯二胺为原料,SBA/NiCl2为催化剂,在超声条件下合成了喹喔啉衍生物,其结构经1H NMR和IR确证。考察催化剂类型、原料摩尔比和催化剂的用量对产率的影响。在最佳条件(苯偶姻和邻苯二胺物质的量比为1.0/1.0,催化剂用量为苯偶姻的10 mmol%,于70℃超声反应5 min)下,产率可达94.7%。     

重庆市江津区空气污染指数变化特征及影响因素分析

以2010~2014年重庆市江津区两个环境空气自动监测站逐日空气污染指数(API)、主要污染因子和空气质量级别为基础,分析了近5年该区空气质量变化特征.结果表明,重庆市江津区城市空气质量总体上以优、良天数为主,主要污染因子为可吸入颗粒物.API从时间变化上看,冬季空气质量最差,春秋季次之,夏季最好.气象因子、地理条件以及人类活动对城区空气质量影响显著.     

Chiral sulfur-containing ligands for iridium(I)-catalyzed asymmetric transfer hydrogenation of aromatic ketones

New efficient catalyst systems, coupled with IrCl(COD)PPh₃ and chiral [SNNS]-type ligands, were employed in the asymmetric transfer hydrogenation of aromatic ketones under mild reaction conditions. The corresponding optically active alcohols were obtained in high yield and good to excellent enantioselectivities (up to 96% ee). The chiral Ir(I) complexes with the ligands of [SNNS]-type were also prepared and characterized, which showed good enantioselectivity and high activity. The reactions can be performed in air and the catalytic experiments are greatly simplified.     

Divergent synthesis of fused Benzo-xanthene and oxazine derivatives via Cu-catalyst

Cu-Cu₂O combination showed synergic effects in catalyzing intramolecular Ullmann coupling reaction for halo-Betti bases to afford fused benzo-xanthenes from both electron-rich and electron-deficient aromatic systems in good yield under mild reaction conditions. The sterically hindered halo-Betti bases also provided products in excellent yield. Under optimized condition, a gram scale reaction was also performed to afford the product in excellent yield. However, without ortho-halo substituted Betti-bases failed to afford fused benzo-xanthene derivatives. Exploring the reaction optimization without Cu metal, serendipitously it was produced 1,3-oxazine derivatives in excellent yield via intramolecular cross-dehydrogenative coupling (CDC) reaction. Similarly, electron-rich, electron-deficient and sterically hindered Betti-bases provided the products in good to excellent yield under mild condition.     

Air-assisted addition of grignard reagents to olefins. A simple protocol for a three-component coupling process yielding alcohols

Silylmethyl, tertiary-alkyl, alkenyl, and aryl Grignard reagents underwent intermolecular addition to olefins, such as styrenes, conjugated dienes, and enynes under an air atmosphere to give homologated alcohols. For example, (trimethylsilyl)methylmagnesium chloride and alpha-methylstyrene in ether at room temperature under dry air directly furnished 2-phenyl-4-(trimethylsilyl)-2-butanol in good yield. As the Grignard addition to olefins under argon with rigorous exclusion of O2 did not proceed at all, the above reaction should involve a radical mechanism: an alkyl radical generated by the aerial oxidation of the Grignard reagent adds to olefin, which is followed by oxygenation. Representative examples of this transformation, where products were obtained in good to excellent diastereo- or regioselectivity, are also disclosed.     

Metathesis route to bridged metallocenes

A variety of bridged metallocenes of Fe(II), Ru(II), Zr(IV), or Hf(IV) were prepared in good yield by the interannular ring-closing metathesis reaction of 1,1'-diallylmetallocenes using the Ru-carbene catalyst, and the present method was extended to diastereoselective reaction to give dl- or meso-bridged metallocenes with excellent stereoselectivity.     

Unprecedented acetylation of phenols using a catalytic amount of magnesium powder

The acetylation of phenols with acetic anhydride was achieved using a catalytic amount of magnesium metal powder under air and solvent-free conditions to afford corresponding phenyl acetates in excellent yield (up to 98%).     

Solvent-free aromatic C-H functionalisation/halogenation reactions

The solvent-free, palladium-catalysed reaction of anilides with CuCl(2) in the presence or absence of copper acetate yields ortho-chlorinated anilides in good to excellent yields, even on a large scale (100 mmol). By contrast, the equivalent reactions with copper bromide, either solvent free or in 1,2-dichloroethane, in the presence or absence of palladium, under air or inert conditions, gave the products of simple electrophilic bromination. Mechanistic studies highlighted the involvement of palladacyclic intermediates, one of which was characterised crystallographically, which undergo subsequent reaction with copper(II) chloride to yield the chlorinated anilide products.     

Efficient palladium-catalyzed homocoupling reaction and Sonogashira cross-coupling reaction of terminal alkynes under aerobic conditions

An efficient method for palladium-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric diynes is presented. The results showed that both Pd(OAc)(2) and CuI played crucial roles in the reaction. In the presence of 2 mol % Pd(OAc)(2), 2 mol % CuI, 3 equiv of Dabco, and air, homocoupling of various terminal alkynes afforded the corresponding symmetrical diynes in moderate to excellent yields, whereas low yields were obtained without either Pd(OAc)(2) or CuI. Moreover, high TONs (turnover numbers; up to 940 000 for the reaction of phenylacetylene) for the homocoupling reaction were observed. Under similar reaction conditions, cross-coupling of 1-iodo-4-nitrobenzene with phenylacetylene was also carried out smoothly in quantitative yield. However, the presence of CuI disfavored the palladium-catalyzed Sonogashira cross-coupling reactions of the less active aryl iodides and bromides. In the presence of 0.01-2 mol % Pd(OAc)(2), a number of aryl iodides and bromides were coupled with terminal alkynes in good to excellent yields. It is noteworthy that this protocol employs mild, efficient, aerobic, copper-free, and ligand-free conditions.     

An atom efficient route to N-aryl and N-alkyl pyrrolines by transition metal catalysis

The synthesis of N-aryl, N-tosyl, and N-alkyl pyrrolines from allyl alcohols and amines has been developed. The reaction sequence includes a palladium-catalyzed allylation step in which non-manipulated allyl alcohol is used to generate the diallylated amine in good to excellent yield. An excess of allyl alcohol was necessary for efficient diallylation of the amine, where the excess alcohol could be recycled three times. For aryl and tosyl amines, Pd[P(OPh)(3)](4) was used and for benzyl and alkyl amines a catalytic system comprising Pd(OAc)(2), P(n)Bu(3), and BEt(3) was used. Both the electronic properties and the steric influence of the amine affected the efficiency of the allylation. The isolated diallylated amines were transformed into their corresponding pyrrolines by ring-closing metathesis catalyzed by (H(2)IMes)(PCy(3))Cl(2)RuCHPh in good to excellent yield. A one-pot reaction was developed in which aniline was transformed into the corresponding pyrroline without isolating the diallylated intermediate. This one-pot reaction was successfully scaled-up to 1 mL of aniline in which the N-phenyl pyrroline was isolated in 95% yield. The versatility of the reaction in which 3-methyl-1-phenyl pyrroline was prepared in two-steps was demonstrated.     

Synthesis of enantiopure 4-hydroxypipecolate and 4-hydroxylysine derivatives from a common 4,6-dioxopiperidinecarboxylate precursor

tert-Butyl 2-substituted 4,6-dioxo-1-piperidinecarboxylates 4 have been prepared in good yield starting from Boc-Asp-O(t)Bu and other beta-amino acids. By analogy with chiral tetramic acids, their reduction by NaBH(4) in CH(2)Cl(2)/AcOH afforded the corresponding cis-4-hydroxy delta-lactams in good yield and stereoselectivity (68-98% de). In the absence of the A(1,3) strain (reduction of 6-substituted 2,4-dioxo-1-piperidines 7), the cis-4-hydroxy isomer was still obtained as the major product but the de values were consistently lower. 4-Hydroxy-6-oxo-1,2-piperidinedicarboxylate 2a, readily accessible from Boc-Asp-O(t)Bu (three steps, 63% overall yield), has proven to be an excellent building block for the synthesis of cis- and trans-4-hydroxypipecolates 17 and 24 (52 and 36% overall yield, respectively) and for the synthesis of a protected 4-hydroxylysine derivative 29 (41% overall yield).