2-芳基-2,3-二氢4(1H)-喹唑啉酮类化合物的合成

在NaHSO4催化下,以苯甲醛和邻氨基苯甲酰胺为底物,在室温下合成了一系列2-芳基-2,3-二氢-4(1H)-喹唑啉酮类化合物,该反应产率高、操作简单、并且避免使用有毒的金属催化剂.     

自由基加成/关环反应合成1,3-二氢吲哚-2-酮的研究进展

近两年来,关于自由基加成/关环反应合成1,3-二氢吲哚-2-酮的报道屡见不鲜.它们大多以N-芳基取代的丙烯酰胺类化合物为底物,在各种不同的金属、无金属和光的催化作用下,与不同的自由基反应,可以一步生成3,3-二取代的吲哚-2-酮衍生物.该类方法现已成为合成含氮五元杂环的一个重要手段,用来合成1,3-二氢吲哚-2-酮及其衍生物.目前对自由基加成/关环反应合成该类化合物的研究多集中在不同催化手段引发不同的自由基和反应机理上.按催化剂类型的不同,对近年来自由基加成/关环反应合成吲哚-2-酮的研究进展进行了综述.     

1,4-二氢-4-芳基-3,5-吡啶二羧酸酯的合成及表征

基于二氢吡啶化合物的构效关系, 设计了一系列1,4-二氢-4-芳基-3,5-吡啶二羧酸酯新化合物. 含有易于水解基团的1,4-二氢-4-芳基-3,5-吡啶二羧酸酯类化合物在碱性条件下水解合成了重要中间体1,4-二氢-4-芳基-3,5-吡啶二羧酸单酯, 收率93%～99.8%. 该二羧酸单酯与α-溴代芳基乙酮在相转移剂催化下反应合成目标化合物, 收率74%～99%. 中间体和目标化合物经¹H NMR, ¹³C NMR, IR, MS和元素分析等确证.     

4-(4-甲基-苯基)-6-苯基-2,2′-联吡啶铂(Ⅱ)光致产氢研究

本文以氯离子配位的4-(4-甲基-苯基)-6-苯基-2,2′-联吡啶铂(Ⅱ)配合物为光敏剂,Co(dmgH)2pyCl为催化剂,三乙醇胺(TEOA)为电子牺牲体,在pH为8.5的乙腈/水混合溶剂中构建了光致产氢体系.体系光照(λ>400nm)19h后产氢量达到1.8mL,反应的转换数(TON)达到804(vs.光敏剂).     

离子液体中一步合成14-芳基-1,6,7,14-四氢二苯并[a, i]吖啶-1,6-二酮衍生物

室温条件下在离子液体[bmim]BF4中合成了14-芳基-1,6,7,14-四氢二苯并[a, i]吖啶-1,6-二酮类衍生物,该方法具有产率高,反应介质可回收使用,反应底物范围广,反应时间短,操作简单等优点。     

Lewis碱协助的 Lewis酸催化醇脱水合成烯烃及二氢吡喃开环合成2-肉桂基取代1,3-二羰基化合物

醇脱水是合成烯烃的重要方法之一。全球每年约有15%的苯乙烯是通过1-苯乙醇在酸性条件下脱水反应生产。虽然人们对该反应进行了较为深入的研究,但是当使用活性较高的1-苯乙醇衍生物为底物时,由于得到的取代苯乙烯产物具有较高的反应性,在脱水过程中会发生聚合而导致反应选择性降低,因此有必要探索适宜在高活性1-苯基乙醇脱水反应中应用的催化剂体系。
　　本文借助酸碱协同催化方法考察了1-(4-甲氧基苯基)乙醇制备4-甲氧基苯乙烯的反应。发现三苯基磷与 AlCl3构建的 Lewis碱/Lewis酸协同催化体系在硝基甲烷中可以接近定量的收率得到4-甲氧基苯乙烯。 Lewis碱/Lewis酸协同催化体系有效避免了4-甲氧基苯乙烯的二聚现象。底物拓展研究显示该方法具有很好的底物普适性,对多种取代苯乙烯的收率均超过80%。机理研究表明,1-(4-甲氧基苯基)乙醇在酸作用下先生成碳正离子,三苯基磷作为偶极性的电子给体不但能在一定程度上稳定该苄基碳正离子,而且抑制了其与4-甲氧基苯乙烯之间的亲电反应,进而最大化了脱质子生成4-甲氧基苯乙烯的选择性。
　　将Lewis碱协助的 Lewis酸催化提高反应选择性策略用于2-苯基-3,4-二氢吡喃衍生物合成2-肉桂基-1,3-二羰基化合物的开环反应。该类取代二氢吡喃在酸催化剂作用下也可生成苄基碳正离子,但是该中间体易受分子间和分子内亲电反应影响,反应选择性不高。而当使用单质碘/三苯基磷协同催化体系时,2-苯基-3,4-二氢吡喃衍生物能高选择性地实现开环反应,得到反式2-肉桂基-1,3-二羰基化合物。该类1,3-二羰基化合物具有丰富的反应性,是一类重要的合成子。     

可见光促进的酰胺氮自由基参与的分子内氢胺化反应

报道了可见光促进的邻烯基取代苯甲酰胺的分子内自由基氢胺化反应.在该反应中,通过脱质子光致电子转移策略实现了氮-氢键的直接催化活化来产生氮自由基,随后通过氮自由基与烯烃的加成来实现氢胺化反应.该反应以优异的收率合成了一系列具有潜在生理活性的3,4-二氢异喹啉酮衍生物.该反应体系利用有机染料催化剂EosinY Na作为光氧化还原催化剂、廉价易得的NaOH作为碱试剂、反应条件温和、操作简单、且官能团兼容性好.另外,该反应在放大量到克级规模、或者利用太阳光作为光源,均能以优异的收率得到相应目标化合物.因此,这类反应为3,4-二氢异喹啉酮的合成提供了一个简便有效的方法.     

MCM-41负载钴催化H_2O_2氧化四氢萘合成α-四氢萘酮

比较了醋酸溶液中过渡金属(Fe、Co、Ni、Ce、Cu、La、Zr或Cr)掺杂MCM-41催化过氧化氢氧化四氢萘合成α-四氢萘酮的转化率和选择性,发现其中Co/MCM-41的催化活性最好。探讨了Co/MCM-41作催化剂时反应温度、反应时间、催化剂用量等对四氢萘氧化的转化率和形成四氢萘酮选择性的影响,确定了较优的反应条件:m(四氢萘)∶m(催化剂)=12.5∶1;反应温度T=383 K,反应时间8 h。四氢萘的转化率达94.7%,α-四氢萘酮的选择性达到70.3%。在反应体系中,Co/MCM-41是一种固体非均相催化剂。催化剂Co/MCM-41可回收重复使用3次,催化活性基本不变。     

均相体系中铱催化2-取代-1,2-二氢喹啉类化合物的脱氢芳构化

 采用原位制备的铱双膦(或膦氮)配合物在碘存在下催化2-取代-1,2-二氢喹啉、2-甲基-2,3-二氢吲哚、1,4-二氢吡啶及3,4-二氢异喹啉等化合物的脱氢芳构化反应, 并考察了不同金属前体、配体、催化剂用量、溶剂和碘等因素对反应速率和选择性的影响. 结果表明,原位制备的［Ir(COD)Cl］2/(±)-MeO-Biphep在碘的存在下催化2-取代-1,2-二氢喹啉的脱氢芳构化反应速率快, 选择性好,催化剂的用量少; 对1,4-二氢吡啶和2,3-二氢吲哚的催化脱氢芳构化反应则须在高温下进行; 而对 3,4-二氢异喹啉, 即使在加热回流条件下也只有不到5%的转化率. 催化体系中碘的存在可以明显提高反应速率.     

烟酰胺辅酶反应中心结构选择1,4-二氢烟酰胺的热力学和动力学根源

合成了对位取代的1-苯基-1,4-二氢烟酰胺和对位取代的1-苯基-1,2-二氢烟酰胺作为烟酰胺辅酶两种模型物, 分别测定了它们与N-甲基吖啶正离子反应热和活化吉布斯自由能. 通过对其热力学参数和动力学参数的比较发现, 虽然1,2-二氢烟酰胺辅酶模型物与吖啶正离子反应热力学驱动力大于相应的1,4-二氢烟酰胺辅酶模型物与吖啶正离子反应热力学驱动力, 但前者具有很高的活化熵, 从而导致其活化吉布斯自由能反而大于后者. 表明烟酰胺辅酶NADH反应中心结构在其氧化还原循环进化过程中选择1,4-二氢烟酰胺而不是1,2-二氢烟酰胺的根本原因是烟酰胺辅酶反应中心结构二氢吡啶环2位上的氢原子较4位上的氢原子有较大的空间位阻.     

Hydrogen-Atom-Transfer-Initiated Radical/Polar Crossover Annulation Cascade for Expedient Access to Complex Tetralins

A radical/polar crossover annulation between allyl-substituted arenes and electron-deficient alkenes is described. Cobalt-catalyzed hydrogen atom transfer (HAT) facilitates tandem radical C−C bond formation that generates functionalized tetralin products in the face of potentially problematic hydrofluorination, hydroalkoxylation, hydrogenation, alkene isomerization, and radical polymerization reactions. The reactions proceed under mild conditions that tolerate many functional groups, leading to a broad substrate scope. This powerful ring-forming reaction very quickly assembles complex tetralins that are the formal products of the largely infeasible Diels–Alder cycloadditions of styrenes.     

Direct Synthesis of Polysubstituted Aldehydes via Visible‐Light Catalysis

Aldehydes are among the most versatile functional groups for synthetic chemistry. However, access to polysubstituted alkyl aldehydes is very limited and requires lengthy synthetic routes that involve multiple‐step functional‐group conversion. This paper reports a one‐step synthesis of polysubstituted aldehydes from readily available olefin substrates using visible‐light photoredox catalysis. Despite a number of competing reaction pathways, commercial styrenes react with vinyl ethers selectively in the presence of an acridinium salt photooxidant and a disulfide hydrogen‐atom‐transfer catalyst under blue LED irradiation. Alkyl aldehydes with different substitution patterns are prepared in good yields. This strategy can be applied to structurally sophisticated substrates.     

Aerobic photo-oxidative cleavage of the C-C double bonds of styrenes

Carbon tetrabromide enables us to carry out oxidative cleavage of the C-C double bonds of styrenes under aerobic photo-irradiation conditions. Oxidative cleavage of the various β-substituted styrenes produced benzoic acid in good yields. Since this reaction is found to be applicable to the α- or β-substituted styrenes, which showed very low reactivity under our previous cleavage reaction condition with FSM-16 and I₂, this reaction can be used complementarily.     

Epoxidation of styrenes with the peroxidase from the cultured cells of Nicotiana tabacum

An enzyme concerned with the epoxidation of styrenes was isolated from cultured cells of Nicotiana tabacum. The enzyme had peroxidase activity as well as epoxidation activity, and its amino acid sequence showed 89% homology in their 9 amino acid overlap with horseradish peroxidase. In the enzymatic reaction, hydrogen peroxide and p-cresol were necessary and molecular oxygen was the source of the oxygen atom of the epoxide. The enzymatic reaction using a spin trap reagent and monitoring of the reaction with ESR indicated that the epoxidation reaction of styrenes proceeded by a radical mechanism with peroxidase.     

Mild Silver‐Mediated Geminal Difluorination of Styrenes Using an Air‐ and Moisture‐Stable Fluoroiodane Reagent

An air‐ and moisture‐stable fluoroiodane in the presence of AgBF₄ is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the C? F bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium‐isotope‐labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.     

Unlocking Mizoroki–Heck‐Type Reactions of Aryl Cyanides Using Transfer Hydrocyanation as a Turnover‐Enabling Step

A new transfer hydrofunctionalization strategy to turnover H‐M^II‐X complexes has enabled both intra‐ and intermolecular Mizoroki–Heck (MH)‐type reactions of aryl cyanides that are challenging to realize under traditional, basic conditions. Initially, a cascade carbonickelation/MH reaction of 2‐cyanostyrenes was achieved using a key alkyne transfer hydrocyanation step. Mechanistic experiments supported the proposed catalytic cycle, including the turnover‐enabling transfer hydrocyanation step. The reactivity was then extended to the intermolecular MH reaction of benzonitriles and styrenes.     

1,1-Regioselective alkenylboration of styrenes enabled by palladium catalysis

Despite the 1,2-difunctionalization reactions of styrenes have been well developed, the 1,1-regioselective addition reaction remains challenging. We disclose herein a palladium-catalyzed, highly 1,1-regioselective alkenylboration of styrenes by using alkenyl triflates and a diboron reagent as the coupling partners. A wide scope of styrenes derivatives and alkenyl triflates participate this reaction to provide the corresponding allyl boronates with high regioisomeric ratios. The success of this reaction is ascribed to the application of 1,10-phenanthroline-derivated ligand and the addition of ammonium chloride salt. Moreover, acrylate esters can also selectively afford the 1,1-alkenylboration products under the same reaction conditions.     

Copper-catalyzed efficient dithiocyanation of styrenes: Synthesis of dithiocyanates

A novel Cu-catalyzed intermolecular chemoselectivity dithiocyanation of styrenes with ammonium thiocyanate has been developed under mild conditions. This reaction exhibits a wide range of functional-group tolerance in styrenes to afford various dithiocyanates. The reaction mechanism was primarily investigated and a radical process was proposed.     

Radical Heck-type reaction of styrenes with sulfonyl hydrazides on water at room temperature

Herein, metal-free radical Heck-type reaction of styrenes with sulfonyl hydrazides to synthesize vinyl sulfones is developed. The reaction is performed under economical TBAI/TBHP system on water in open air at room temperature, which proceeds through the radical addition to styrenes followed by hydrogen-abstraction. When compared to known approaches for the synthesis of vinyl sulfones from alkenes, this radical Heck-type strategy is practical, green and does not go through HI elimination process. Furthermore, this protocol can be expanded to the iodosulfonylation of alkynes for the synthesis of iodovinyl sulfones.     

Cerium(IV) ammonium nitrate: Reagent for the versatile oxidative functionalization of styrenes using N-hydroxyphthalimide

Cerium(IV) ammonium nitrate was found to be a versatile reagent for the oxidative functionalization of styrenes using N-hydroxyphthalimide and iodine affording three different types of products with oxyphthalimide, nitrate and iodide groups. It was shown that reaction of styrenes with N-hydroxyphthalimide and cerium(IV) ammonium nitrate can be selectively directed to oxynitro-oxyphthalimides and dioxyphthalimides depending on the reaction conditions, in particular a solvent. Reaction of styrenes with iodine under the action of N-hydroxyphthalimide and cerium(IV) ammonium nitrate leads to the formation of iodo-oxyphthalimides.