7-氨基-3-乙烯基头孢烷酸的合成

以7-苯乙酰氨基-3-氯甲基头孢烷酸对甲氧基苄酯为原料经Wittig反应、水解、酶解三步反应合成重要的药物中间体——7-氨基-3-乙烯基头孢烷酸,总收率71.2%。其结构经1H NMR和IR表征。     

氮杂Wittig反应的最近进展

综述了最近几年氮杂Wittig反应的研究进展,包括分子间氮杂Wittig反应、分子内氮杂wittig反应及串联的氮杂Wittig反应。讨论了氮杂Wittig反应在一些含氮杂环、稠杂环及天然产物合成中的应用。     

Synthesis of Related Compounds of Carotenoid

类胡萝卜素是一类奇特的色素，由高等植物和微生物光化学合成，作为防止单线氧通过光敏反应产生危害的必要基团，类胡萝卜素最近受到了关注。类胡萝卜素联于富勒烯上，既可大大增加在可见光区域光诱导电子转移的有效吸收断面，又可抑制富勒烯敏化单线氧的危害能力。合成了类胡萝卜素的相关化合物，报道的某些反应条件先进且简洁。     

S-甘油醛缩丙酮的合成及其Wittig反应

以L-抗坏血酸为原料合成了S-甘油醛缩丙酮;研究了S-甘油醛缩丙酮的Wittig反应立体选择性.     

Solvent reduced wittig olefination reactions with halo containing conjugated phosphoranes

The Wittig reaction of carbaldehydes with alkoxycarbonylhalomethylidenetriphenylphosphoranes can be performed with ease in solventless systems. The analogous reaction of carbaldehydes with acylhalomethylidenetriphenylphosphoranes requires a small amount of solvent, such as chloroform, in order for the reaction to proceed. The products of the reaction are versatile precursors for further transformations, such as the Suzuki-Miyaura cross-coupling reaction.     

Synthesis of linear monodisperse vinylene-linked phenothiazine oligomers

A series of linear monodisperse vinylene-linked phenothiazine oligomers have been synthesized by alternate Heck reaction and Wittig reaction in good yields. It was found that their absorption and fluorescence emission bands red-shifted with increasing phenothiazine units due to extending of the conjugated degree. The fluorescent quantum yield increased from OPTZ1 to OPTZ6, and the Φ_F of OPTZ6 was close to phenothiazine-based polymers.     

A novel ambident reactivity of azolylacroleins

Reaction of azolylacroleins with phosphoranes bearing a conjugated double bond was found to yield either azolyltrienes in a Wittig reaction, or to undergo cyclization to a dihydrobenzene containing the azole substituent. Transformation with an aza-Wittig reagent gave tetrazolylpyridines. The ambident reactivity was found to be dependent on the substituent of the phosphorane, which was rationalized by ab initio (DFT) calculation of the atomic charges of the reaction centres.     

新型2-氨基-5-苯亚甲基-4H-咪唑啉-4-酮衍生物的合成及生物活性

通过烯基膦亚胺1与芳基异氰酸酯的aza-Wittig反应得到碳二亚胺2,再用2与亲核试剂的成环反应制得10个新型的2-氨基-5-苯亚甲基-4H-咪唑啉-4-酮衍生物4,探讨了碳二亚胺2与不同亲核试剂反应的活性并分离得到了一个胍中问体3i,初步研究了化合物4的生物活性.     

Synthesis of 2S-(2-hydroxyethyl)-3R-hydroxy-4S-(thymin-1-yl or adenin-9-yl)-tetrahydrofuran

Two synthetic strategies were developed to obtain isonucleosides 2a and 2b. Starting from the known compound 4, an extension of one carbon unit at sugar 6-terminal was achieved by Wittig reaction and Stannyl-desulfonylation reaction. After oxidation of the double bond, the isonucleosides with elongated side chain 2a and 2b were synthesized. For the synthesis of isonucleosides containing different bases, an epoxide intermediate approach was developed. Isonucleosides 2a and 2b were synthesized by regioselective epoxide opening reaction of 18 in good yield.     

Nucleosides and nucleotides. 191 : Ring expansion reaction of 1-[2,3,5-tri-o-TBS-4α-formyl-β-D-ribo-pentofuranosyl]uracil by treating with (methylene)triphenylphosphorane to give a new nucleoside containing dihydrooxepine ring at the sugar moiety

When 1-[2,3,5-tri-O-TBS-4α-formyl-β-D-ribo-pentofuranosyl]uracil (5) was treated with (methylene)triphenylphosphorane in THF, an unusual ring-expansion reaction occurred to give a nucleoside (7) containing dihydrooxepine ring at the sugar moiety. A deuterium-label experiment showed that one carbon unit derived from the ylide was incorporated into the 5'-position of 7. A ring cleavage between the C-3' and C-4' of 5 during the reaction was suggested.     

含氟磷亚胺化合物的合成及其氮杂-Wittig反应的初步研究

以氟烷基叠氮化合物为原料,合成了含氟磷亚胺化合物,并对其氮杂-Wittig反应进行初步研究,通过^1H NMR,^19F NMR,IR,MS及元素分析对化合物的结构进行了表征。     

Chemo- and regioselectivity in the reactions of polyfunctional pyrroles

The chemo- and regioselectivity of the reduction, oxidation and Wittig reaction of polyfunctional pyrroles, containing a variety of reactive centres was investigated. The reaction of 3,5-dichloropyrrole-2,4-dicarboxaldehydes with potassium permanganate leads to regioselective oxidation of the 2-formyl group, while the Wittig reaction with 1 equiv of a triphenylphosphorane produced the 2-alkenyl substituted pyrroles.     

应用不同交联度的聚合物Wittig试剂合成亚洲玉米螟性信息素

我国广东省测试分析中心及美国的Klun几乎同时确定亚洲玉米螟性信息素的化学结构为(E)及(Z)-12-十四碳烯-1-醇乙酸酯(Z:E=1:1)。合成方法大多由合适的炔烃出发,先合成相应的炔键类似物,再转化成烯键,但原料较难获得,反应条件苛刻,路线长或产率     

A convenient synthesis of olefins via deacylation reaction

A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room temperature in high yields (70-90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig, Wittig-Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the α-substituents of the 1,3-dicarbonyl compounds.     

A convenient method for the preparation of α-vinylfurans by phosphine-initiated reactions of various substituted enynes bearing a carbonyl group with aldehydes

α-Vinylfurans were obtained by phosphine-initiated cyclization of various enynes bearing a carbonyl group at the ene end in the presence of various aldehydes, in moderate to high yields. The reaction may consist of 1,6-addition of phosphine to the enynes, ring closure, and Wittig reaction between the ylid resulting from cyclization and an aldehyde. Thus, various aldehydes were able to be used in the reaction. The reaction was influenced greatly by the substituents at the acetylene position (R¹) and the α-position of the carbonyl group (R³).     

Base-Promoted Elimination Reactions of Acetaldehyde N-Alkyl-N,N-Dimethylhydrazonium Salts. A Convenient Synthesis of N,N-Dimethylalkylamines

The title reaction was utilized for efficient conversion of S_N2-reactive alkyl halides to the corresponding N,N-dimethylaIkylamines.     

A One-Pot and Convenient Synthesis of Coumarins in Solventless System

An efficient and facile preparation of simple coumarins via in situ Wittig reaction of salicylaldehydes, triphenylphosphine, and chloroethylacetate supported on MgO in satisfactory yields in solvent-free condition.     

Novel Base‐Free Catalytic Wittig Reaction for the Synthesis of Highly Functionalized Alkenes

A highly efficient catalyst system for base‐free catalytic Wittig reactions has been developed and optimized. Initially, several potential (pre)catalysts as well as different silanes as reducing agents were screened. A system based on a readily available phosphine oxide as precatalyst and trimethoxy silane as reducing agent proved to be optimal. The effect of various Brønsted acidic additives was studied. Subsequently, the reaction conditions were optimized and standard reaction conditions were determined. Under these conditions the scope of this new protocol was evaluated. Nine activated olefins and 33 aldehydes were converted into 42 highly functionalized alkenes. Notably, aromatic, aliphatic as well as heteroaromatic aldehydes could be converted, giving the desired products in isolated yields up to 99 % and with good to excellent E/Z selectivities. These results underline the remarkable efficiency of this protocol considering the complexity of the reaction mixture and the four reaction steps that proceed in parallel in one pot.     

Stereoselective synthesis of the common polyketide fragment of hoiamides

Stereoselective synthesis of the polyketide fragment commonly present in hoiamide A, B, and C is described using iterative Crimmins aldol reaction as the key reaction.     

One-Pot Wittig and Knoevenagel Reactions in Ionic Liquid as Convenient Methods for the Synthesis of Coumarin Derivatives

Efficient synthesis of a variety of 3-substituted coumarins via NaOMe-catalyzed Knoevenagel condensation and one-pot preparation of 3,4-unsubstituted coumarins in the presence of NaOMe via Wittig reaction in room-temperature ionic liquids are described. Knoevenagel condensation of 2-hydroxybenzaldehyde with dimethyl- and diethylmalonate was performed with excellent yields in room-temperature ionic liquids. Although diethyl- and dimethylchloromalonates were mostly recovered unchanged in Knoevenagel condensation, higher conversions were observed via Wittig reaction of these compounds with 2-hydroxybenzaldehyde derivatives and triphenylphosphine. Other 2-hydroxybenzaldehyde derivatives, methyl- and ethylchloroacetates, were reacted in ionic liquids to afford simple coumarins in good yields. These reactions widen the applicability of ionic liquid in organic synthesis.