金属锡作用下烯丙基溴与α,β-不饱和醛、酮和醌的反应

金属锡作用下烯丙基溴与α,β-不饱和醛区域选择性加成,只生成1,2-加成产物。烯丙基卤代物和锡与1,4-醌类反应,不经分离,直接氧化可得到烯丙基取代醌类。     

金属锡作用下烯丙基溴与α,β-不饱和醛、酮和醌的反应

金属锡作用下烯丙基溴与α,β-不饱和醛区域选择性加成,只生成1,2-加成产物.烯丙基卤代物和锡与1,4-醌类反应,不经分离,直接氧化可得到烯丙基取代醌类.     

烯丙基溴与锡和醛的选择性加成反应

Yamamoto等曾报道烯丙基型的锡有机化合物可与羰基化合物进行亲核加成反应,得到高烯丙基型的醇.他们还发现此反应具有立体选择性.此后又发现这个反应可以被溶剂中的微量水所催化,使反应加速进行.这些结果促使我们进一步探讨当醛分子中含有羟基、酚基、硝基、卤素等各种不同的反应活性基团时,与烯丙基锡进行的反应.希望找到一种用传统的Grignard试剂无法直接进行的烯丙基化反应. 我们选择了间和邻羟基苯甲醛、间和对硝基苯甲醛、对溴苯甲醛、7-羟基-3,7-二甲基辛醛等化合物作反应底物,在金属锡粉存在下使羰基化合物与烯丙基溴反应.结果都得到了相应的高烯丙基醇.     

钐试剂在合成中的应用 Ⅱ.金属钐作用下烯丙基卤代物与酯的反应

在金属钐的作用下,烯丙基卤代物与酯反应,生成α,α-二烯丙基叔醇,其中,与γ-丁内酯反应,开环生成4-烯丙基-6-庚烯-1,4-二醇     

α-卤代酮和羰基化合物在碘化钾/金属盐作用下的碳-碳双键形成反应

本工作研究了α-卤代酮与羰基化合物之间在易得试剂碘化钾和某些硬路易斯酸的金属盐, 如三氯化铝, 四氯化钛等复合作用下形成碳碳双键, 生成(E)-α,β-不饱和羰基化合物的反应。     

2-氯甲基苯并恶唑的Darzens反应研究

本文报道用2-氯甲基苯并恶唑作为卤代物,进行Darzens反应。义固体氧化钾作碱,在非质子极性溶剂N,N-甲基酰胺中,将其与相应的羰基化合物反应, 生成了环氧化合物。     

α-卤代酮与芳香二胺经氧化-缩合过程一锅法合成喹喔啉衍生物

在二甲亚砜作用下, α-卤代酮与芳香1,2-二胺反应, 得到较高产率的喹喔啉衍生物. 结果表明反应经历一个串联的氧化-缩合过程. 二甲亚砜现场氧化α-卤代酮, 生成的二羰基化合物与芳香1,2-二胺缩合成喹喔啉衍生物.     

二碘化钐在有机合成中的应用研究

综述了1998年以来二碘化钐在有机合成中的应用研究，主要涉及羰基化合物、 不饱和烃、卤代物、腈及含氧族元素化合物的特殊反应．     

纳米铝粉促进羰基化合物水相烯丙基化反应

氮气保护条件下,纳米铝在0.1 N NH₄Cl溶液中,能有效地促进羰基化合物与烯丙基溴进行Barbier-Grignard型烯丙基化反应,得到相应高烯丙醇。芳香族醛或酮的烯丙基化产率较高,而脂肪族羰基化合物反应产率低,反应产率受羰基空间位阻影响大,在同样条件下,邻羟基羰基化合物烯丙基化产物主要是赤式-邻二醇。     

立体选择性地合成（E）—β,γ—不饱和酸酯的新方法

α-芳基和α-烯基羰基结构是一类天然产物的重要结构特征。一种简便的方法将极大地有利于这些分子的合成。β,γ-不饱和酸酯属这种结构的一部分。目前,这方面已有一些工作。其中,较重要的有烯丙基化合物在催化剂作用下与一氧化碳及醇类反应成酯法,卤代烯烃与金属试剂催化偶联法及α,β-共轭     

A repertoire of pyridinium-phenyl-methyl cross-talk through a cascade of intramolecular electrostatic interactions

Direct intramolecular cation-pi interaction between phenyl and pyridinium moieties in 1a(+) has been experimentally evidenced through pH-dependent (1)H NMR titration. The basicity of the pyridinyl group (pK(a) 2.9) in 1a can be measured both from the pH-dependent chemical shifts of the pyridinyl protons as well as from the protons of the neighboring phenyl and methyl groups as a result of electrostatic interaction between the phenyl and the pyridinium ion in 1a(+) at the ground state. The net result of this nearest neighbor electrostatic interaction is that the pyridinium moiety in 1a becomes more basic (pK(a) 2.92) compared to that in the standard 2a (pK(a) 2.56) as a consequence of edge-to-face cation (pyridinium)-pi (phenyl) interaction, giving a free energy of stabilization (DeltaDeltaG(o)pKa) of -2.1 kJ mol(-1). The fact that the pH-dependent downfield shifts of the phenyl and methyl protons give the pK(a) of the pyridine moiety of 1a also suggests that the nearest neighbor cation (pyridinium)-pi (phenyl) interaction also steers the CH (methyl)-pi (phenyl) interaction in tandem. This means that the whole pyridine-phenyl-methyl system in 1a(+) is electronically coupled at the ground state, cross-modulating the physicochemical property of the next neighbor by using the electrostatics as the engine, and the origin of this electrostatics is a far away point in the molecule-the pyridinyl-nitrogen. The relative chemical shift changes and the pK(a) differences show that the cation (pyridinium)-pi (phenyl) interaction is indeed more stable (DeltaDeltaG(o)pKa = -2.1 kJ mol(-1)) than that of the CH (methyl)-pi (phenyl) interaction (DeltaDeltaG(o)pKa = -0.8 kJ mol(-1)). Since the pK(a) of the pyridine moiety in 1a is also obtained through the pH-dependent shifts of both phenyl and methyl protons, it suggests that the net electrostatic mediated charge transfer from the phenyl to the pyridinium and its effect on the CH (methyl)-pi (phenyl) interaction corresponds to DeltaG(o)pKa of the pyridinium ion (approximately 17.5 kJ mol(-1)), which means that the aromatic characters of the phenyl and the pyridinium rings in 1a(+) have been cross-modulated owing to the edge-to-face interaction proportional to this DeltaG(o)pKa change.     

Chalcogenide-Lewis acid mediated reactions of electron-deficient alkynes with aldehydes

Reactions of but-3-yn-2-one (2) with aldehydes 1 in the presence of a Lewis acid and dimethyl sulfide (3 a) predominantly gave (E)-alpha-(halomethylene)aldols 4-5 in high yields, while reactions of methyl propiolate (6 a) mainly afforded (Z)-3-halogeno-2-(hydroxymethyl)acrylates 7-8 in low to moderate yields. A reaction of dimethyl acetylenedicarboxylate (10) with 1 a in the presence of TiCl(4) and 1,1,3,3-tetramethylthiourea (3 c) produced maleate (E)-11 (40 %) and butenolide 12 (40 %). When a reaction of 6 a with 1 a was carried out in the presence of TiBr(4) and 3 a (0.2 equiv) at -20 degrees C for 60 h, 3-(methylthio)-2-(hydroxyalkyl)acrylate 9 a was obtained in an 8 % yield. Experiments were conducted in order to elucidate the formation mechanism of 9 a, and it was made clear that 9 a was formed via the processes of the Michael addition of sulfide 3 a to alkynoate 6 a and an aldol reaction with 1 a and demethylation.     

Synthesis of phthalide derivatives using nickel-catalyzed cyclization of o-haloesters with aldehydes

The reaction of o-bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3-phenyl-3H-isobenzofuran-1-one (3 a) in an 86 % yield. Similarly, o-iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4-MeC(6)H(4)CHO; 2 c, 4-MeOC(6)H(4)CHO; 2 d, 3-MeOC(6)H(4)CHO; 2 e, 2-MeOC(6)H(4)CHO; 2 f, 4-CNC(6)H(4)CHO; 2 g, 4-(Me)(3)CC(6)H(4)CHO; 2 h, 4-C(6)H(5)C(6)H(4)CHO; 2 i, 4-ClC(6)H(4)CHO; 2 j, 4-CF(3)C(6)H(4)CHO; 2 k, CH(3)(CH(2))(5)CHO; 2 l, CH(3)(CH(2))(2)CHO) also underwent cyclization with o-bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2-bromo-4,5-dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six-membered lactones. The reaction of methyl 2-(2-bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six-membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.     

Origin of Aldehydes in Sediments of Qinghai Lake

This paper has analysed the aldehyde fractions in sediments and living organisms of Qinghai Lake using GC-MS and discussed their origin, n-Aldehydes detected in the sediments ranged from C_(16) to C_(32) with a maximum at C_(22) C_(24) or C_(26) and showed a strong even over odd predominance. n-Aldehydes in the living organisms analysed ranged from C_(16) to C_(32) with a maximum at C_(26) or C_(28). The authors believed that aldehydes in modern sediments may directly derive from biosynthesis.     

Micellization of copolymers via noncovalent interaction with TPPS and aggregation of TPPS

Aggregation of 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin (TPPS) was investigated in complex micelles composed of poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP) and poly(2-(dimethylamino)ethyl methylacrylate)-b-poly(Nisopropylacrylamide) (PDMAEMA-b-PNIPAM) in aqueous solutions.The resultant complex micelles had a complex P4VP/ PDMAEMA/TPPS core and a mixed PEG/PNIPAM shell.Different noncovalent interaction modes between the porphyrin and each copolymer accomplished a co-effect on the ...     

Synthesis and reaction of alpha-dithiolactone

Treatment of di-tert-butylthioketene S-oxide (5 a) with Lawesson reagent at room temperature resulted in the formation of 3,3-di-tert-butylthiirane-2-thione (4 a) in high yield. The oxidation of 4 a with mCPBA (mCPBA=m-chloroperbenzioc acid) gave 3,3-di-tert-butylthiirane-2-thione S-oxide (6) almost quantitatively. The reactions of 4 a with dimethyl acetylenedicarboxylate (DMAD) and benzyne afforded dimethyl 2-(2,2,4,4-tetramethylpentan-3-ylidene)-1,3-dithiole-4,5-dicarboxylate (13) and 2-(2,2,4,4-tetramethylpentan-3-ylidene)benzo[d][1,3]dithiole (15), respectively, in high yields, suggesting that 4 a is an excellent 1,3-dipole. The reaction of 4 a with ethylenebis(triphenylphosphine)platinum (16) gave dithiolato-platinum complex (22) in high yield. The structure of 22 was determined by X-ray crystallographic analysis.     

Origin of Ketones in Sediments of Qinghai Lake

This paper analysed the ketone fractions in sediments and living organisms of Qinghai Lake using GC-MS and discussed their origin,n-Alkan-2-ones detected in the sediments ranged from C_(12) to C_(33) with a maximum at n-C_(25) or n-C_(29) and showed a strong odd predominance, n-Alkan-2-ones in the living organisms analysed ranged from C_(15) to C_(31) with a maximum at n-C_(27).The authors believed that ketones in modern sediments may directly derive from biosynthesis.     

Solubilization of triglycerides in liquid crystals of nonionic surfactant

The solubilization of triglycerides [1,2,3-tributanoylglycerol (TBG) and 1,2,3-trihexanoylglycerol (THG)] in water/octa(oxyethylene) dodecyl ether (C(12)EO(8)) systems has been investigated. Oil-induced changes in the structure of liquid crystals in water/C(12)EO(8) system have been studied by optical observation and small-angle X-ray scattering (SAXS) measurements. In the water/C(12)EO(8)/oil systems, solubilization of THG and TBG induces a transition between H(1) (hexagonal) and L(alpha) (lamellar) liquid crystals at high C(12)EO(8) concentrations, whereas at low surfactant concentrations a H(1)-I(1) (discontinuous micellar cubic phase) transition occurs. This anomalous behavior is attributed to the partitioning of solubilized oil in the micelles. At low surfactant concentrations THG is mainly solubilized into the hydrophobic cores of the surfactant micelles, indicating high swelling or low penetration tendency, resulting in a steep increase in the radius of the aggregates (r(H)), thereby inducing a rod-sphere transition. At high surfactant concentrations, THG is not mainly solubilized into the core but distributed between the palisade layer and the core of the aggregates. The TBG is considerably solubilized into the surfactant palisade layer, indicating a high penetration tendency, resulting in an increase in the effective cross-sectional area per surfactant molecule, a(s). The thermal stability of the I(1) phase increases with the solubilization of THG into the aggregate cores. The percentage deviation of the experimental interlayer spacings (P(d)) from complete swelling was also evaluated for different triglycerides in the H(1) and L(alpha) phases or different surfactant concentrations. It is found that the penetration tendency of triglycerides could be used as a tuning parameter for I(1) phase formation depending on the surfactant concentration and the molecular weight of the oil.     

Reactions of meso-hydroxyhemes with carbon monoxide and reducing agents in search of the elusive species responsible for the g = 2.006 resonance of carbon monoxide-treated heme oxygenase. Isolation of diamagnetic iron(II) complexes of octaethyl-meso-hydroxyporphyrin

To examine possible models for the g = 2.006 resonance seen when the hydroxylated heme-heme oxygenase complex in the Fe(III) state is treated with CO, the reactivities of CO and reducing agents with (py)(2)Fe(III)(OEPO) and [Fe(III)(OEPO)](2) (OEPO is the trianion of octaethyl-meso-hydroxyporphyrin) have been examined. A pyridine solution of (py)(2)Fe(III)(OEPO) reacts in a matter of minutes with zinc amalgam (or with hydrazine) under an atmosphere of dioxygen-free dinitrogen to produce bright-red (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O, which has been isolated in crystalline form. The (1)H NMR spectrum of (py)(2)Fe(II)(OEPOH) in a pyridine-d(5) solution is indicative of the presence of a diamagnetic compound, and no EPR resonance was observed for this compound. Treatment of a solution of (py)(2)Fe(II)(OEPOH) in pyridine-d(5) with carbon monoxide produces spectral changes after a 30 s exposure that are indicative of the formation of diamagnetic (OC)(py)Fe(II)(OEPOH). Treatment of a green pyridine solution of (py)(2)Fe(III)(OEPO) with carbon monoxide reveals a slow color change to deep red over a 16 h period. Although a resonance at g = 2.006 was observed in the EPR spectrum of the sample during the reaction, the isolated product is EPR silent. The spectroscopic features of the final solution are identical to those of a solution formed by treating (py)(2)Fe(II)(OEPOH) with carbon monoxide. Addition of hydrazine to solutions of (OC)(py)Fe(II)(OEPOH) produces red, diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py in crystalline form. The X-ray crystal structures of (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O and (OC)(N(2)H(4))Fe(II)(OEPOH).py have been determined. Solutions of diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py and (OC)(py)Fe(II)(OEPOH) are extremely air sensitive and are immediately converted in a pyridine solution into paramagnetic (py)(2)Fe(III)(OEPO) in the presence of dioxygen.     

Electrosynthesis of hydroquinonethioethers using electrochemical oxidation of hydroquinone in the presence of thiouracil derivatives

Electrochemical oxidation of hydroquinone(1a) has been studied in the presence of 6-methyl-2-thiouracil(3a) and 6-propyl-2-thiouracil(3b) as nucleophiles in a DMF/buffer mixture,using cyclic voltammetry and controlled-potential coulometry.The results indicated that the p-quinone(2a) derived from 1a participates in a 1 4-Michael addition reaction with the thiouracil derivatives(3a–b) to form the corresponding hydroquinonethioether derivatives(6a–6b).The electrosynthesis of these compounds(6a–b) has been successfully performed on carbon rod electrodes in an undivided cell in good yield and purity.