An efficient synthesis of quinazoline-2,4-dione derivatives with the aid of a low-valent titanium reagent

A facile synthetic method using low-valent titanium reagent (TiCl₄/Zn system) to promote the novel reductive cyclization of 2-nitrobenzamides and triphosgene is described. Sequentially, a series of quinazoline-2,4-diones were synthesized in good yields.     

Selective reduction of carbonyl groups in the presence of low-valent titanium reagents

The chemoselective reduction of several structurally diverse compounds containing carbonyl groups was achieved in the presence of low-valent titanium reagents. This novel synthetic method provides easy access to highly selective reduction of carbonyl groups, and possesses several advantages including one-step procedure, convenient manipulation, good to excellent yields, and short reaction times.     

Reductive coupling of aliphatic cyclic imides with benzophenones by low-valent titanium

The reductive coupling of aliphatic cyclic imides with benzophenones by Zn–TiCl₄ in THF gave two- and four-electron reduced products selectively by controlling the reaction conditions. Although cyclic and acyclic products were formed as mixtures in most cases, cyclic dehydrated products could be selectively obtained by heating the product mixtures in the presence of cat. p-TsOH.     

Reductive coupling of 1,3-dimethyluracils with benzophenone by low-valent titanium: unusual two-to-one coupling

The reductive coupling of 1,3-dimethyluracil with benzophenone by Zn-TiCl₄ in THF gave unusual two-to-one adduct and its further reduced product. The reductive coupling of 1,3-dimethyl-5-fluorouracil with benzophenone by Zn-TiCl₄ also gave two-to-one adduct. 1,3-Dimethylthymine was, however, completely inert under the same conditions.     

Reductive coupling of isatins with ketones and aldehydes by low-valent titanium

The reductive coupling of isatins with ketones and aldehydes by Zn–TiCl₄ in THF gave two- and four-electron reduced products, 3-hydoxy-3-(1-hydoxyalkyl)oxindoles and 3-alkylideneoxindoles, selectively by controlling the reaction conditions. Although the 3-(1-hydoxyalkyl)oxindoles were also produced as the four-electron reduced products in some cases, these products were readily dehydrated to 3-alkylideneoxindoles. The 3-alkylideneoxindoles derived from aldehydes were formed as mixtures of geometric isomers. The both geometric isomers were isomerized to the equilibrium mixtures by reflux in cat. PPTS/benzene.     

An efficient one-step synthesis of 2-arylquinolin-4(1H)-ones with the aid of a low-valent titanium reagent

A short and facile synthesis of a series of 2-arylquinolin-4(1H)-ones was accomplished in good yields via the novel reductive cyclization of 2-nitrochalcones promoted by TiCl₄/Zn. This method has the advantages of accessible starting materials, one-step procedure, convenient manipulation, and moderate to high yields.     

Reductive coupling of hydantoins with benzophenones by low-valent titanium: Synthesis of 4-substituted 1H-imidazol-2(3H)-ones and unusual two-to-two coupled products

The reductive coupling of 1,3-dimethyhydantoin with benzophenones by TiCl₄-Zn in THF gave 4-diarylmethyl-1H-imidazol-2(3H)-ones as four-electron reduced one-to-one coupled products and their dimers as two-to-two coupled products predominantly by controlling the reaction conditions. The reductive coupling of 5-alkyl-1,3-dimethyhydantoins with benzophenones produced 5-alkyl-4-diarylmethyl-1H-imidazol-2(3H)-ones as the sole products irrespective to the reaction conditions. On the other hand, the reductive coupling of 1,3-dimethyhydantoin with cyclic benzophenones selectively 4-arylhydroxymethyl-1H-imidazol-2(3H)-ones as two-electron reduced one-to-one coupled products and they were further reduced to 4-diarylmethyl-1H-imidazol-2(3H)-ones.     

Highly regioselective synthesis of polysubstituted pyrroles through three-component reaction induced by low-valent titanium reagent

1,2,3,5-Tetrasubstituted and 1,2,3,4,5-pentasubstituted pyrroles may be synthesized through three-component reaction of 1,3-diketones, aldehydes, and amines induced by low-valent titanium reagent. High regioselectivity was achieved. Compared with the classical synthetic method, this new method has the advantages of short reaction time (15 min), high yields, convenient manipulation, and high regioselectivity.     

An efficient synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent

An efficient and improved synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent (TiCl₄/Zn) is described. In this reaction triethylamine (TEA) was used to control the pH value. This method has the advantages of easily accessible starting materials, convenient manipulation, higher yield, shorter reaction time, and wider substrate scope.     

Asymmetric Epoxidation of Methyl Gibberellate by the Modified Sharpless Reagent

Asymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent in the various temperature is described. Compound 8 and 9 can be used as the key intermediates for synthesis of the polyhydroxygibberellins.     

钛醇盐电化学合成的研究

采用钛金属为“牺牲”阳极,首次在无隔膜电解槽中,电化学一步法制备了纳米TiO~2前驱体钛醇盐Ti(OEt)~4,Ti(OPr-i)~4,Ti(OBu)~4。产物通过元素分析、红外光谱(FT-IR)、拉曼光谱进行表征。电化学一步法直接制备纳米材料前驱体钛醇盐,克服了传统化学方法合成金属醇盐步骤多、产率低、纯度达不到要求及后续分离繁琐等缺点。本文同时讨论了影响电合成钛醇盐的关键因素及可能的反应机理,实验表明钛在醇溶液中呈点蚀行为,钛醇盐卤化物Ti(Ⅲ)(OR)~nBr~m在阳极形成,然后被氧化为Ti(Ⅳ)(OR)~nBr~m,这种物质在阴极上ROH参与下被还原生成钛醇盐Ti(OR)~4,钛阳极表面拉曼光谱证实了上述观点。防止阳极钝化,温度控制在50～60℃之间,彩有机胺溴化物为导电盐,可以提高电合成收率。     

Cyclization of α-haloamide with internal double bond by use of the low-valent metal complex

The α-haloamide having internal double bond was allowed to react with a catalytic amount of Pd(PPh₃)₄ in the presence of proton sponge to produce a cyclized product in a fairly good yield possibly through the intermediation of σ-alkylmetal complex although it was not isolated.     

Direct ethoxycarbonyldifluoromethylation of aromatic compounds using Fenton reagent

Direct ethoxycarbonyldifluoromethylation of aromatic compounds by BrCF₂CO₂Et was investigated using Fenton reagent in dimethylsulfoxide. Various five-membered hetero-aromatic compounds, benzene derivatives and uracil having ethoxycarbonyldifluoromethyl group were obtained catalytically with the combination of ferrocene and H₂O₂ at room temperature. The ethoxycarbonyldifluoromethylation occurred at the position predicted by the trend of the electrophilic substitution of aromatic compounds. When para-substituted aniline derivatives were used as a substrate, the one-pot synthesis of 3,3-difluoro-2,3-dihydroindole-2-one derivatives was achieved through the ethoxycarbonyldifluoromethylation at the ortho-position to the amino group and the consecutive intramolecular amidation of the amino group and the adjacent ethoxycarbonyldifluoromethyl group.     

An effective route for the synthesis of cationic palladium complexes of general formula [(Acac)PdLL]A

A series of palladium complexes of general formula [(Acac)PdL¹L²]⁺A⁻, where L¹, L² = phosphines and A = BF₄, CF₃SO₃, were synthesized. Preliminary studies show that the complexes are active in selective dimerization of styrene and addition polymerization of norbornene.     

低价钛促进的1,2-二氢喹唑啉-4(3H)-酮的合成

喹唑啉-4(3H)-酮是一类生物碱,取代喹唑啉-4(3H)-酮具有广泛的药理学活性．因而对其合成方法和合成新型喹唑啉-4(3H)-酮的衍生物的研究已成为热点．低价钛试剂是一种还原偶联试剂,它能引起醛酮的还原偶联生成烯烃,还能引起其它官能团的还原偶联反应,该反应已应用于天然产物和一些碳环化合物的合成,而用于杂环化合物的合成研究报道较少．本文报道低价钛试剂(TiCl4-Zn体系)促进的1,2-二氢喹唑啉-4(3H)-酮的合成。     

Chelating dialkoxide titanium complex: a versatile building block for the construction of heterometallic derivatives

The heterometallic complex [TiCp*(O(2)Bz)(2)AlMe(2)] (2) has been synthesised by reaction of [TiCp*(O(2)Bz)(OBzOH)] (1) with AlMe(3) (Cp*=eta(5)-C(5)Me(5); Bz=benzyl). Complex 1 reacts with HOTf to yield the cationic derivative [TiCp*(OBzOH)(2)]OTf (3) (HOTf=HSO(3)CF(3)). Compound 3 reacts with [{M(mu-OH)(cod)}(2)] (M=Rh, Ir; cod=cyclooctadiene) to render the early-late heterometallic complexes [TiCp*(O(2)Bz)(2){M(cod)}(2)]OTf (M=Rh (4); Ir (5)). The molecular structure of complex 4 has been established by single-crystal X-ray diffraction studies.     

火花放电原子发射光谱法测定钛及钛合金中主要元素

采用火花放电原子发射光谱法测定了钛及钛合金中碳、铁、铝和钒的含量。通过对钛合金样品的表面处理方式、氩气流量和压力、类型标准化等参数的摸索,确立了一套系统的分析方法。结果表明,4种元素测定的相对标准偏差在0.40%~6.8%,测定结果和化学湿法分析结果相比基本一致,比较适合批量检测。     

低价钛促进的苯并咪唑并[1,2-c]喹唑啉衍生物的合成

利用低价钛试剂促进的2-邻硝基苯基苯并咪唑与原甲酸酯或丙酮或固体光气的反应, 合成了一系列苯并咪唑并[1,2-c]喹唑啉衍生物, 化合物的结构经IR, 1H NMR, MS和元素分析确定, 化合物4c的结构经单晶X射线衍射分析进一步确证. 该方法具有原料易得、操作简便和产率高等优点.