A Novel Entry to the Eremophilane and Valencane Sesquiterpenes via a Stereoselective Intramolecular Diels-Alder Reaction. Preliminary communication

A general stereoselective entry to racemic eremophilane and valencane sesquiterpenes, via a common key intermediate and using an intramolecular Diels-Alder reaction, is described.     

Intramolecular Diels-Alder Reaction of Thioaldehydes

Intramolecular Diels-Alder reaction of thioaldehydes which were generated from bis(trimethylsilyl) sulfide and dienals gave the corresponding bicyclic adducts.     

Studies on the Synthesis of Eremophilane Sesquiterpenes. A Novel Entry into the Aristolane Ring System

Readily available tricyclo[3.2.2.0^2,4]non-6-en-8-one is converted into the tricyclo ring system of the aristolane sesquiterpenes via an alkoxide accelerated [3, 3]-sigmatropic rearrangement.     

A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives

The reaction between the chiral allenic acid (+)-(S)- 1 and the carbodiimides 2a – d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3 – 5 , 7 , and 8 . Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.     

内分子DIELS-ALDER反应合成DRIMANE类倍半萜化合物DRIMENIN, POLYGODIAL及CINNAMOLIDE的全合成

近年来有不少报道从事于生理活性Drimane类倍半萜的合成,较多采用了分子间Diels-Alder反应来建立Drimane的骨架。本文首次采用内分子Diels-Alder反应作为关键反应合成了Drimane类化合物。同时还在引入了手性诱导基团后,首次完成了从无手性的原料化合物β-紫罗兰酮至光学活性(-)-drimenin1的不对称合成。     

Approach to Animated Anthracyclines via an Intramolecular Marschalk Reaction

An anionic cyclization based approach to a novel daunomycin analog is described.     

Synthesis of Antitumor Lycorines by Intramolecular Diels-Alder Reaction

Pharmacologically interesting lycorines were obtained by a short, efficient method based on an intramolecular Diels-Alder reaction between an alpha-pyrone and an alkyne, followed by loss of CO(2) in a retro Diels-Alder reaction. The cyclization precursors (pyrones 9) were obtained in good yields in two or three steps from the corresponding homophthalic acid or anhydride.     

Formal Total Synthesis of (+)-Dihydromevinolin via a Chelate-Controlled Intramolecular Diels-Alder Reaction as the Key Step

Compound 3 was synthesized efficiently from enone 4 via (silyloxy)cyclopropanecarboxylate intermediates 6 and 7 . A chelate-controlled intramolecular Diels-Alder reaction of 3 afforded the octahydronaphthalene-2-carboxylate isomer trans- 2b as the main product. This compound was stereoselectively converted into the known dihydromevinolin precursor 1 , thus providing a formal total synthesis of this natural product.     

The Type 2 Intramolecular Diels-Alder Reaction: Synthesis and Chemistry of Bridgehead Alkenes

Anti-Bredt alkenes, bicyclic molecules that contain a bridgehead double bond, were for many years regarded as chemical curiosities. The type 2 intramolecular Diels-Alder (IMDA) reaction provides a one-step entry into this fascinating class of molecules. The reaction has made available numerous anti-Bredt alkenes for structural and chemical studies. X-ray crystallography has revealed the magnitude of the deformations associated with the bridgehead double bond, and rate studies of reactions of bridgehead alkenes have allowed quantification of the kinetic consequences of the torsional distortions. More recently, the type 2 intramolecular Diels-Alder reaction and the resulting anti-Bredt alkenes have found application in organic synthesis. The constraints resulting from the connectivity in the Diels-Alder precursor creates a strong regio- and stereochemical bias in the cycloaddition step. The end result of this bias is the stereoselective synthesis of highly substituted six-membered rings. The reaction also achieves a facile synthesis of seven- and eight-membered rings in a single step from acyclic precursors. The utility of this reaction has been verified in recent applications of the type 2 IMDA reaction as a key step in the total synthesis of complex natural products.     

Intramolecular Diels-Alder Reaction of Cyclohexa-2,4-dienones: Synthesis and Photochemical Reactions of Oxa-Homobrendanes

Synthesis of Oxa-homobrendanes having β, γ-unsaturated carbonyl chromophore and their photoreactions in singlet (¹S) and triplet (³T) excited states leading to novel bowl shaped molecules have been reported.     

利用分子内Click反应合成哌嗪并三唑和哌嗪并四唑化合物

利用分子内的"点击化学"反应合成了三唑和四唑类化合物。在直接加热或金属铜粉催化下加热的条件下,不饱和炔键和氰基与叠氮基发生分子内的成环反应,以较高的收率分别生成哌嗪并三唑化合物和哌嗪并四唑化合物,其结构经NMR,IR和MS表征。     

A New Enantioselective Total Synthesis of Natural Vincamine via an Intramolecular Mannich Reaction of an Silyl Enol Ether

Natural Vincamine ( 1 ) has been synthesized in an enantioselective manner starting from the ethylpentenal 7 . In the key step a mixture of the diastereoisomeric racemates, 14 and 15 , was directly obtained from the silyl enol ether 11 and the dihydro-β-carboline 12 by the way of an intramolecular Mannich reaction of the intermediate 13 (Scheme 4). The undesired stereoisomers, 14 and 15b , were recycled to 15a using the related reversible Mannich reaction 18 ? 14 + 15 , followed by crystallization of the salt from 15a and (+)malic acid. 15a was converted to natural vincamine ( 1 ) in several steps including the known transformation 20→1 .     

Diels-Alder反应可控制备交联等规聚丙烯

交联改性可以提升聚合物材料的机械性能、热稳定性及化学稳定性。 含有蒽基团的高质均分子量等规聚丙烯(iPP)可由配位共聚合反应制得,随后通过双官能的马来酰亚胺试剂与iPP中悬挂蒽基团间的Diels-Alder反应可以成功制备交联的iPP膜材料。 材料的交联度可以通过凝胶重量分析及膜红外分析得出,并由制备过程中交联剂的加入量有效地调控。 通过示差扫描量热仪(DSC)与广角X射线衍射仪(WAXD)表征发现,随交联度增加,交联改性限制了分子链的运动,iPP的结晶度逐渐降低、结晶能力逐渐下降。 对交联材料的动态热机械分析仪(DMA)测试表明,随交联度增加,iPP的损耗模量逐渐降低,材料韧性变差。 交联iPP的T_g逐渐升高,说明材料的耐热性得到提升。 由于交联形成了聚合物链间的交联网络,形成了更多受力点并且限制了聚合物链的自由移动,交联材料的拉伸强度随交联度的升高而增加,而断裂伸长率逐渐下降。     

A Study of Intramolecular Diels-Alder Reactions of Allylamino Dienenitriles

The intramolecular Diels-Alder reactions of 2-allylanilino 3,5-heptadienenitriles (3) produced equimolar amounts of perhydroisoindoles 4 and 5, the structures of which were determined by spectral methods, but also by X-ray diffraction of 4a.