NaOH与TEAH催化熔融酯交换合成聚碳酸酯及其重排产物研究

分别以NaOH和氢氧化四乙基铵(TEAH)为催化剂,碳酸二苯酯(DPC)和双酚A(BPA)为原料,采用熔融酯交换法合成聚碳酸酯.当DPC与BPA的摩尔比为1.05∶1,催化剂与BPA的摩尔比为5×10-4∶1时,在所采用的工艺条件下,可分别得到Mn、Mw/Mn为1.69×104、1.97(NaOH催化),1.23 × ...     

Indium-mediated Reformatsky-Claisen rearrangement

A new variant of the Reformatsky-Claisen rearrangement is described. The reaction of substituted allyl α-bromoacetates with indium and indium(III) chloride under ultrasonication provides a general entry into the functionalized synthon.     

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.     

A new pathway via intermediate 4-amino-3-fluorophenol for the synthesis of regorafenib

A practical synthetic route to regorafenib, in which the target compound was obtained via a 10-step synthesis starting from 2-picolinic acid, 4-chloro-3-(trifluoromethyl)aniline, and 3-fluorophenol, is reported. Crucial to the strategy is the preparation of 4-amino-3-fluorophenol via Fries and Beckman rearrangements using an economical and practical protocol. The main advantages of the route include inexpensive starting materials and an acceptable overall yield. A scale-up experiment was carried out to provide regorafenib with 99.96% purity in 46.5% total yield.     

A Concise Total Synthesis of (+)‐Tetrabenazine and (+)‐α‐Dihydrotetrabenazine

Highly concise asymmetric total syntheses of (+)‐tetrabenazine ( 1 ), a drug for the treatment of chorea associated with Huntington’s disease, and of (+)‐α‐dihydrotetrabenazine ( 2 ), an active metabolite of 1 , have been accomplished. Our synthetic route features a trans‐selective enol etherification, followed by an unprecedented cation‐dependent aza‐Claisen rearrangement to establish the carbon framework and two stereogenic centers of tetrabenazine. The syntheses consist of seven steps (34 % overall yield) for (+)‐ 2 and eight steps (22 % overall yield) for (+)‐ 1 .     

A facile and stereoselective synthetic method for allylic 1,3-dienyl ethers

The 1,4-elimination reaction of 1-allyloxy-4-methoxy-(2Z)-alkenes with n-butyllithium is shown to proceed in a marked preference to the [2,3] Wittig rearrangement to afford the allylic (1Z,3E)-dienyl ethers in high stereoselectivities. The synthetic utility of this method is demonstrated by the Claisen rearrangement of the dienyl ethers thus obtained.     

（E,E）—3,7—二甲基—2,6—癸二烯—1,10—二醇的高立体选择？…

1969年 Meinwald等 [1] 从一系列雄性蝴蝶的“hair pencils”中分离得到一组信息素成分 ,包括一类新颖的开链倍半萜骨架化合物 1— 3.尽管这些化合物在结构上与香叶醇相似 ,但利用香叶醇为原料进行合成的报道 [2～ 5] 还不多见 .本文以香叶醇为原料 ,报道了化合物 3的一条简便、高立体选择性的合成路线 .其关键反应步骤是 2 ,3-环氧醇的碘代重排反应和烯丙基烯基醚的克莱森重排反应 .a.Ac2 O,Pyridine,r.t.,2 h,yield 98% ;b.Se O2 ,t-Bu OOH,CH2 Cl2 ,r.t.,3 h,yield 73 % ;c.VO( acac) 2 ,t-Bu OOH,reflux,2 h,yield 90 % ;d.Ph3…     

Transformations of lignans. Part 10: Acid-catalysed rearrangements of arboreol and wodeshiol and conversion of gmelanone oxime into a dihydropyranone derivative

The synthesis of gmelanone 2 by a pinacol-type rearrangement of arboreol 1 supports its biogenesis and confirms its relative and absolute configuration. The further transformation of gmelanone oxime 12 into the dihydropyranone oxime 13 supports the intermediacy of gmelanone like intermediates in the rearrangements of furofuran lignans to pyran derivatives. In contrast, acid-catalysed rearrangement of wodeshiol 7 affords the dihydropyranone 8.     

新型异戊烯并环黄酮化合物的合成

以间苯三酚和3,3-二甲基烯丙酸为起始原料,通过苄基保护、甲基化、脱保护基、Clemmenson还原、乙酰化、Fries重排、Baker-Venkataraman重排和成环等10步反应, 以18.2%的总收率合成了1个新型异戊烯并环黄酮化合物BE-1C,其结构经¹H NMR, ¹³C NMR和HR-MS(ESI-TOF)表征。     

A flexible approach to hexahydronaphthalene-1-carboxylates

A flexible approach to hexahydronaphthalene-1-carboxylates based on the Favorskii rearrangement of 1,1-dichloro bicyclo[5.4.0]undec-5-en-2-ones has been devised. 1,1-Dichloro bicyclo[5.4.0]undec-5-en-2-ones can be prepared from readily available cyclohexanones by a short sequence.     

芳氨基硫脲类化合物的质谱研究（Ⅱ）

本文报道了五种新的芳氨基硫脲类化合物，即１－（４－溴－２－羧基苯基）－４－烷基氨基硫脲的电子轰击质谱（ＥＩＭＳ）。结果表明，该类化合物的分子离子峰（Ｍ＋）很弱，但却具有效强的［Ｍ－Ｈ］＋峰。分子离子的断裂以Ｎ－Ｎ键和Ｃ－Ｎ键的断裂为主，并伴随着六员环或四员环过渡态氢重排，生成相应的芳氨基正离子和芳肼基正离子，这两种离子继续失水或失其它小分子，从而形成一系列特征离子，包括骨架重排离子。     

Enantioselective and collective syntheses of xanthanolides involving a controllable dyotropic rearrangement of cis-β-lactones

Let's swap: a scalable, atom-economic, enantio-, and diastereoselective synthetic route to trisubstituted γ-butyrolactones based on a Wagner-Meerwein-type dyotropic rearrangement of cis-β-lactones is described. This methodology was applied in efficient and protecting-group-free formal syntheses and total syntheses of various xanthanolide natural products.     

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.     

Semipinacol and protoadamantane-adamantane rearrangements of 5,6-dibromoadamantan-2-one and -2-ol

A number of new polybrominated adamantanes were formed by rearrangements and bromination of 2,2,6,6-tetrabromoadamantane under Friedel-Crafts conditions. Protoadamantane-4,10-dione, 10-acetoxyprotoadamantan-4-one, 1,2,6-triacetoxyadamantane and 5,6-diacetoxyadamantan-2-one were formed by successive semipinacol and protoadamantane-adamantane rearrangements of 5,6-dibromoadamantan-2-one and 5,6-dibromoadamantan-2-ol. This work may open up new pathways for the synthesis of 1,2,6-trisubstituted adamantanes.     

A Practical Domino‐Claisen–Cope Sequence in the Synthesis of New Blooming Citrus and Potent Floral Rose Alcohols

Fifty years after its first discovery by Alan Francis Thomas , we describe a versatile, metal and pressure‐free domino‐Claisen–Cope rearrangement using the readily available α ,β‐unsaturated aldehydes 5 or their acetals 5′ and allylic alcohols 6 . This transformation provides a convenient access to a large number of radiant citrus and floral rosy odorants. Odor profiles of novel floral rosy and citrus alcohols 13 , 14 , and 16 were studied. Compound 14ba has a floral, rosy, geranium‐like character and shows unique performance and diffusiveness. Compound 16ba has a clear main citrus odor character with a clean green grapefruit/rhubarb connotation. Both odorants have been successfully introduced to perfumery recently as Rosyfolia ™ ( 14ba ) and Pomelol ™ ( 16ba ).