低价钛化合物催化合成咪唑烷的一锅合成法

本文报道了在低价钛催化下,亚胺类化合物和原甲酸三乙酯发生交叉偶联反应以适中产率制得咪唑烷类化合物,并对所得各种不同取代基的咪唑 烷基化合物的产率和异构体比例进行了讨论。产物的构型用核磁共振波谐进行了表征。     

超声波作用下羰基化合物的还原偶联反应

超声波在一些有机反应中有明显的促进作用「“，Luche等认为超声波的作用有两种主要类型［’j．一类是涉及电子转移的自由基或离子一自由基型反应，由于超声波的空化作用所产生的局部高温高压可以促进电子转移，从而明显地加快反应速度；对大多数离子型反应，超声波只能起到机械的物理作用．我们曾报道偕二卤化合物在Li、Na、Mg等金属作用下产生卡宾的反应是单电子转移过程，该反应可由于超声辐射而大大加速［‘］；而在芳基叔脚的断裂反应中，超声波可以促进三苯基俄与金属馊反应生成二苯基脚负离子，但对它进一步的亲核取代反应却没有明…     

An Efficient Preparation of 2, 3-Disubstituted Indole Derivatives Induced by Low-valent Titanium

An efficient synthesis of 2, 3-disubstituted indole derivatives through low-valent titanium induced reductive cyclization of acylamido carbonyl compounds is described.     

Efficient Synthesis of 2-Arylbenzothiazole Derivatives with the Aid of a Low-Valent Titanium Reagent

A novel and facile synthesis of 2-arylbenzothiazole derivatives was accomplished in good yields via the novel reductive cyclization of bis-(2-benzalaminophenyl)disulfide promoted by the TiCl₄/Sm system. The advantages of this new method are the easily accessible starting materials, short reaction time, and moderate to good yields.     

低价钛盐还原反应的研究——Ⅱ.低价钛盐与芳基三卤甲烷的反应

用LiAlH_4或Zn、Mg等与四氯化钛作用得到的低价钛盐能使芳基三卤甲烷还原偶联为1,1,2,2-四卤-1,2-二芳基乙烷、1,2-—二卤-1,2-二芳基乙烯或二芳基乙炔,反应可能生成ArCX_2·自由基,然后偶联为二芳基四卤代乙烷,后者能脱去卤素生成二芳基二卤代乙烯。TiCl_3和Ti°与三氯甲苯作用能得到相似的后果。     

TiCl4-Cr还原偶联活泼卤化物及芳醛、芳酮的研究

低价钛化合物在有机合成和有机反应中有着广泛的应用。我们曾研究了低价钛对α,α,α-三卤甲基苯的脱卤偶联、对2,2-二芳     

低价钛引起的羧酸衍生物与芳酮的还原偶联反应

本文报道了在低价钛试剂作用下羧酸衍生物与芳酮的还原偶联反应.     

TiCl~4-Ga还原体系中芳基三卤甲烷的还原偶联反应

研究了在低价钛(TiCl~4-Ga)试剂作用下,α,α,α-三卤甲基芳烃的还原偶联反应,得到了脱卤偶联产物-二卤代烯烃、炔烃。     

低价钛诱导的羰基还原偶合反应在西松烷型二萜天然产物全合成中的应用

概述了低价钛诱导的羰基还原偶合反应作为环化关键步骤在西松烷型二萜天然产物全合成中的应用。参考文献26篇。     

Organocatalytic Enantiospecific Total Synthesis of Butenolides

Biologically important, chiral natural products of butenolides, (−)-blastmycinolactol, (+)-blastmycinone, (−)-NFX-2, (+)-antimycinone, lipid metabolites, (+)-ancepsenolide, (+)-homoancepsenolide, mosquito larvicidal butenolide and their analogues were synthesized in very good yields in a sequential one-pot manner by using an organocatalytic reductive coupling and palladium-mediated reductive deoxygenation or organocatalytic reductive coupling and silica-mediated reductive deamination as the key steps.     

活性钛与芳基丙酮的还原偶合反应

羰基化合物还原偶合是形成碳-碳键的一种重要方法。本文首次发现此类反应的产物不仅与反应物本身的结构和还原试剂体系有关，还与操作次序有很大关系，且在活性钛表面反应。     

Synthesis and Crystal Structure of 3,5-Diphenyl- 1,2- di（4- chlorophenyl）pyrrole

1 INTRODUCTION The pyrrole ring constitutes a basic heteroaro- matic structure. It is a vital building block for the construction of porphyrins and alkloids[1]. Several substituted pyrroles have potential applications as fungicides and bactericides and as active compo- nents of nonsteroidal anti-inflammatory drugs inhi- biting human cyclooxygenase[2, 3]. Besides the clas- sical Knorr’s method, there are a number of poten- tially useful methods for the synthesis of pyrrole he- terocyclic …     

Total synthesis of pyridovericin

The total synthesis of the naturally occurring kinase inhibitor pyridovericin 1 is reported. A flexible and efficient synthesis has been accomplished in good yield from readily available 2,4-dihydroxypyridine. Pyridovericin is a key intermediate in our proposed biomimetic synthesis of pyridomacrolidin 2.     

Titanium‐Catalyzed Reductive Umpolung Reactions with a Metal‐Free Terminal Reducing Agent

A new method for titanium‐catalyzed reductive umpolung reactions is reported that overcomes the traditional requirement for a stoichiometric metallic reductant. With N,N′‐disilylated tetramethyldihydropyrazine as a potent organic reducing agent, reductive carbonyl–nitrile, enone–acrylonitrile and pinacol coupling reactions can be achieved in good yields and stereoselectivities. [Cp₂TiI₂] is a superior catalyst to [Cp₂TiCl₂], which is rationalized by a faster generation of the active catalyst [Cp₂TiI]. A mechanism is proposed that is in agreement with the experimental results.     

Synthesis and Crystal Structure of 2,2- Pentamethylene-1,2,3,4-tetrahydroquinazolin-4-one

1INTRODUCTIONIntheearlyseventiesthreegroupsofinvesti-gators[1～3]establishedthatlow-valenttitaniumcanabstractoxygenfromketonesoraldehydes,leadingtotheformationofolefins.Avarietyofotherfunc-tionalgroupscanalsobereduced[4～7].However,thereactionof2-nitroben…     

低价钛在有机合成中的应用新进展

主要综述了近年来低价钛诱导的McMurry反应在有机合成中的应用新进展.     

Total synthesis of mycestericin A and its 14-epimer

The total synthesis of mycestericin A (1) and its 14-epimer 34 is described herein. The Overman rearrangement of an allylic trichloroacetimidate derived from l-tartrate generated a tetra-substituted carbon with nitrogen and subsequent stereoselective transformations afforded the highly functionalized left-half segment, vinyl iodide. Cross-coupling of the vinyl iodide with a chiral organometallic species synthesized from d-tartrate under the Negishi or Suzuki-Miyaura coupling conditions, followed by deprotection, completed the total synthesis of 1. The 14-epimer of mycestericin A was also synthesized, and a comparison of [α]_D values of peracetyl γ-lactone derivatives of mycestericin A and its 14-epimer as well as degradation studies of 1 and 34 fully confirmed the proposed absolute structure of mycestericin A.