烷氧基重排反应

本文综述了烷氧基重排反应.根据不同的反应机制,可将烷氧基重排反应分为三类:通过碳正离子重排的烷氧重排反应,分子内烷氧基亲核取代反应和烷氧O-迁移反应.     

TMSCl促进的分子内亲核取代反应合成α-亚烷基-哌啶酮

以烯基碘代物为底物,丁基锂为锂代试剂,THF为溶剂,在TMSCl促进下通过分子内亲核取代反应合成了4个α-亚烷基-哌啶酮(2a~2d),其结构经~1H NMR,~(13)C NMR和HR-MS(ESI)确证。在最优反应条件(1 2 mmol,n-Bu Li 2.4 mmol,TMSCl 3 mmol,THF 20 m L,于170℃反应1 h)下,2a~2d收率68%~84%。     

碳正离子重排反应合成Cyclocitrinol核心骨架

Cyclocitrinol是一类具有独特的桥环结构的天然产物,其桥环核心骨架可由高张力的降蒈烯酮开环制备得到.以商品化的19-羟基雄甾为原料,通过高烯丙基碳正离子重排反应,高效地合成了降蒈烯酮关键中间体,完成了Cyclocitrinols天然产物的核心骨架的合成.     

分子内氮原子上亲核取代反应的理论研究

Using the -CHR-(CH2)3-NFCH3(R=H, CH3, CH2CF3, CHO, COCH3) as the computational model, the two possible intramolecular reactions, nucleophilic substitution on nitrogen and elimination reaction, were studied at the theoretical level of MP2(full)/6-31+G(d,p). The results indicate that the elimination mechanism, when the -CHR radical is more basic (R=H, CH3, CH2CF3) leading to linear products R-CH2-(CH2)3N=CH2 is preferred. In contrast, electro-withdrawing groups CHO and COCH3 on the attacking site will favor the intramolecular nucleophilic substitution of nitrogen and form 5-membered heterocyclic compounds. These theoretical predictions agree with the available experiments.     

对甲苯磺酸吡啶盐催化乙酸烯丙酯的烷氧基取代/重排反应

以对甲苯磺酸吡啶盐为催化剂,实现了乙酸烯丙酯的烷氧基取代/重排反应,收率60%～95%.产物的结构经1H NMR表征.     

环庚烷正离子重排反应的从头算研究

先采用HF方法,基组采用STO-3G,对环庚烷正离子的重排机理进行了初步粗略的从头算研究,较快地找到了反应过程中的部分过渡态。然后再采用MP2/3-21G方法精确计算了整个重排过程中的各个过渡态的几何构型、零点能,同时对反应路径也进行了计算,以作进一步的过渡态验证。得出的结论是:环庚烷正离子的重排是环的缩小过程,在生成甲基环己烷叔正碳离子的过程中,经历了2个过渡态;首先是C(1)C(7)的键长变长、C(1)C6的键长变短,β位H(20)逐渐远离与之相连的C(1),与C(7)形成化学键;然后是与C+相连的H(16)逐渐远离C+,与β位的C(1)形成化学键,产生稳定的甲基环己烷叔正碳离子椅式结构,甲基环己烷叔正碳离子还有可能进一步重排为一个含伯正碳离子的甲基环己烷结构,计算了每一步重排反应所需的活化能。     

Bamberger重排反应的拓展研究

N-烷氧基-N-芳基酰胺在不同的反应条件下,既可经历保留或脱去酰基的重排反应,也可在芳烃的邻位或对位选择性地引入各类亲核试剂,并已成功地应用于天然物的全合成.     

关于扩环反应产物预测常见错误的讨论

扩环反应是近几年国内、国际化学竞赛的热门考点。通过对2个典型扩环反应产物预测错误的分析，揭示、总结产生错误的原因，并给出正确判断产物的参考思路。     

基于“芳香亲核取代-重排”机理检测生物活性分子的荧光探针

生物硫醇包括谷胱甘肽(GSH)、半胱氨酸(Cys)和同型半胱氨酸(Hcy),在生理过程中扮演着不同的重要角色,其分布和浓度的异常变化常与多种疾病的病理过程息息相关.由于生物硫醇结构和反应活性的相似性,对它们的选择性检测极具挑战.近年来,“芳香亲核取代-重排”机理发展成为生物硫醇选择性检测的通用策略,并扩展到其他生物活性分子的检测.本文根据探针荧光团和检测物的不同进行分类,综述了基于“芳香亲核取代-重排”机理的荧光探针的设计、合成与应用进展.     

己二烯基烯丙基醚的Wittigσ迁移重排反应

烯丙基醚类的[2.3]Wittig σ迁移重排反应是近几年来新发展的一个有机合成反应。由于此反应具有高度的非对映选择性和立体选择性,它为合成中的碳链延伸、立体选择性反应及不对称合成提供了一个新的方法,因为此反应可通过选择底物的几何构型和取代基得到立体选择性产物。[2.3]Wittig σ迁移重排     

Intramolecular Diels-Alder Reaction of Furans with Allenyl Ethers Followed by Phenylthio and Trialkylsilyl Groups Rearrangement

A new reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by phenylthio group rearrangement was discovered. Treatment of the propargyl ethers 2a-c with t-BuOK in t-BuOH at 85 ° C gave the phenylthio group rearrangement products 5a-c and 6a-c . A reaction involving an intramolecular Diels-Alder reaction of a furan diene with an allenyl ether dienophile followed by trialkylsilyl group rearrangement is also demonstrated.     

Nucleophilic Rearrangement of Functionally-substituted 2-Ethylpyridines

The nucleophilic rearrangement of 2'-substituted 2-ethylpyridines by the action of methylamine was studied. When the side chain has a nitrile group, the rearrangement is accompanied by intra- and intermolecular ammonolysis, leading to cyclic and linear amides, respectively. When the side-chain has an indole substituent, the rearrangement proceeds through the classical scheme.     

烷氧基取代金属酞菁的合成及其吸收光谱性质

合成了６种烷氧基取代的酞菁化合物，并进行了元素分析．研究了它们在溶液和薄膜中的吸收光谱性质．     

轴向为烷氧基配位的萘酞菁硅配合物的光谱及光稳定性

轴向为烷氧基配位的萘酞菁硅配合物的光谱及光稳定性;萘酞菁硅;轴向烷氧基配位;光谱性质;光稳定性     

Chiral DMAP‐N‐oxides as Acyl Transfer Catalysts: Design,Synthesis, and Application in Asymmetric Steglich Rearrangement

A DMAP‐N‐oxide, featuring an α‐amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O‐acylated azlactones afforded C‐acylated azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee). Compared to the widespread use of pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyl transfer reaction, we discovered that chiral DMAP‐N‐oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyl transfer catalysts. Our finding might open a new door for the development of chiral DMAP‐N‐oxides for asymmetric acyl transfer reactions.     

Chiral Alkoxy Side Chains from (-)-Amino Acids in Mediating Asymmetric Synthesis of Tricarbonyl(cyclohexadienyl)iron Complexes

The asymmetric induction in the complexation reaction of (S)-1-methyl-2-(5-methyl-cyclohexa-1,4-dienylmethyloxy)-pyrrolidine 5 and (S)-2-(2-N,N-dimethylamino-1-propanoxy)-5-methylcyclohexa-1,4-diene 6 having heteroatom adjacent the stereogenic center has been investigated. The diastereoselectivity was determined directly from the diastereotopic peaks in the ¹H NMR or by chemical correlation with 9 . The conversion of η-1,4-complexes 7a and 8a to 9 proceeded with high retention of configuration while that of the η-2,5-Fe(CO)₃ complexes 7b and 8b undergoes considerable racemization.     

可见光催化诱导的Smiles重排研究进展

Smiles重排反应是有机合成中被广泛使用的人名反应之一, 是芳基化合物构建策略的一种独特方法. Smiles重排经历了近一个世纪的发展, 从传统的离子型Smiles反应、Truce-Smiles反应等, 发展到后期的自由基型Smiles重排, 这些进展极大地丰富了该反应在合成化学、材料化学等领域的应用. 近年来, 光催化氧化还原反应获得了广泛关注, 这一新颖催化模式高效利用光能, 能在温和的条件下产生自由基中间体, 实现了很多选择性反应. 过去的五年中, 化学家逐渐将这一催化模式应用到了Smiles重排反应中, 发展了一系列新颖、实用的合成方法. 本文对这些进展进行综述, 主要依据促进重排反应的自由基种类和成键类型进行分类.     

Rearrangement process occurring in the fragmentation of adefovir derivatives

The fragmentation of the antiviral drug adefovir dipivoxil and its two active metabolites, adefovir and monopivoxil adefovir, was investigated using both ion trap and triple-quadrupole mass spectrometers. Fragment ions due to loss of 30 Da were observed and attributed to an unanticipated rearrangement process by loss of formaldehyde. The proposed mechanism is supported with the aid of three newly synthesized adefovir derivatives and with accurate mass measurement. Other fragmentations by loss of a pivaloyl group, loss of water, C-P bond cleavage and C-O bond cleavage were also observed for adefovir derivatives. It was concluded that the compounds containing a >POO-CHR-OCO- group generally displayed a rearrangement reaction by loss of RCHO in collision-induced dissociation, and the process generally required an activation energy lower than for a direct bond cleavage.     

Asymmetric Organocatalytic Rearrangement Reactions

Rearrangement reactions often lead to the regio‐ and stereoselective formation of carbon–carbon or carbon–heteroatom bonds, and allow the construction of otherwise hard‐to‐access molecular frameworks. Research disclosed in the present decade, especially in the last two years, has shown that organocatalytic modes of activation can be successfully applied to a variety of rearrangements. In this Minireview we discuss the advances achieved so far in asymmetric organocatalytic rearrangement reactions.     

Synthesis of Chiral Crownophanes Having Two Phenolic Groups via Tandem Claisen Rearrangement and Their Chiral Recognition

Asymmetric crownophanes having a chiral binaphthyl unit and two phenolic hydroxyl groups were thermally synthesized from the corresponding macrocyclic ethers via tandem Claisen rearrangement. Circular dichroism (CD) spectroscopic studies and HPLC experiments confirmed that little racemization of these crownophanes occurred during the thermal rearrangement. The association constants for the interaction of the chiral crownophanes with the enantiomers of phenylethylamine, phenylglycinol, and phenylalaninol were determined by a ¹H NMR titration method in CD₂Cl₂. As a result, the 27 membered crownophane has some chiral recognition for phenylglycinol.