Alkynylzirconation of alkynes and application to one-pot bisalkynylation of alkynes

Stereocontrolled alkynylzirconation of unactivated alkynes was achieved by the reaction of an alkyne with Cp2ZrEt2 and alkynyl halide in this order. After hydrolysis of the alkynylzirconation product, trisubstituted enyne derivatives were obtained in good yields. Functionalized enynes were also prepared by the reaction of the alkynylzirconation products with a variety of electrophiles. Subsequent addition of the second alkynyl halide to the alkynylzirconation products provided an in situ protocol for bisalkynylation of alkynes into (Z)-enediynes in good yields.     

Synthesis of Ketone from Alkyl Halide Using α-Chloro Nitrone as Oxidizing Reagent: A New Approach

Consecutive S_N2 reaction of α-chloronitrones were studied with isopropyl halides, and the nitrones have remarkable oxidizing properties for the conversion of isopropyl halides to ketones with good yields. In addition, the side product obtained can serve as efficient dipolarophile in 1,3-dipolar cycloaddition reaction to produce spiro cycloadduct in good yield.     

Reaction of zirconacyclopentadienes with electrophiles such as benzaldehyde, methyl methacrylate and 1-bromo-2-butyne after treatment with RLi

Zirconacyclopentadienes reacted with electrophiles after treatment with alkyllithium. For example, the reaction with benzaldehyde after treatment with methyllithium to give a nucleophilic addition product of a dienyl moiety to aldehyde, dienylcarbinol, in a moderate yield. Similar reaction of a zirconacyclopentadiene using butyllithium with methyl methacrylate afforded a Michael addition product in a good yield. Treatment of zirconacyclopentadienes with n-BuLi followed by 1-bromo-2-butyne gave a mono-propargylated diene derivative in 95% yield after hydrolysis. When propargyl chloride was treated with n-BuLi first and then added to zirconacyclopentadienes, penta-substituted benzene derivatives were formed in high yields.     

Enantioselective conjugate addition of silylketene acetals to beta-enamidomalonates. Synthesis of beta-amino acid derivatives

[reaction: see text] Conjugate addition of silylketene acetals or enolsilanes to enamidomalonates proceeds with excellent chemical efficiency and good selectivity using Cu(OTf)2 and a chiral bisoxazoline. The effect of the Lewis acid, ligand, the N-acyl substituent, and the nucleophile on yield and selectivity for the addition product have been evaluated.     

Reaction of perfluorocyclopentene with various carbon nucleophiles--heteroaromatic lithium reagents, enolate and phosphonium ylide

The addition of heteroaromatic lithium reagents 2 to a THF solution of perfluorocyclopentene (1) provided preferentially the corresponding monosubstituted products 5, while the addition of 1 to 2 effectively gave the 1,2-disubstituted products 6 in good to excellent yields. The reaction of 1 with sodiomalonate 3 or phosphonium ylide 4 also proceeded smoothly to form the 1,3-disubstituted product 8 or 10 in high yield, respectively.     

Unusual reaction of aryldiazoacetates with enamines: highly effective synthesis of γ-ketoesters

The reaction of aryldiazoacetates with enamines catalyzed by copper and rhodium complexes provided γ-ketoesters in good yields. Careful analysis of the crude reaction mixture revealed a substituted enamine as the primary product, which was hydrolyzed over silica gel to give a γ-ketoester as the final product. A reaction mechanism involving nucleophilic addition of an enamine to a metal carbene and subsequent hydrogen transfer was proposed.     

β-硝基苯乙烯衍生物与二溴海因高度区域选择性氨溴加成反应

以β-硝基苯乙烯衍生物为底物, 二溴海因为氮源/卤素源, 乙腈作溶剂, 建立了碳碳双键上高度区域选择性氨溴加成反应新体系. β-硝基苯乙烯衍生物与二溴海因在室温无水碳酸钠催化下反应, 可高收率获得邻位氨溴加成产物, 最高收率达97%; β-甲基-β-硝基苯乙烯衍生物在氢氧化钾催化下回流反应, 也可高收率得到邻位氨溴加成产物, 最高收率达95%. 实验结果表明, 对于硝基苯乙烯衍生物, 当苯环4-位具有强供电子基团如CH₃O时, 可以得到单一的α-氨基-β-溴加成产物, 但其收率相对较低; 当硝基苯乙烯衍生物的苯环4-位有强吸电子基团如NO₂时, 反应收率则很高. 这一实验结果证明β-硝基苯乙烯衍生物(缺电子烯烃)与二溴海因的氨溴加成反应具有亲核加成的特征. 本文共考察了20种不同结构的β-硝基苯乙烯衍生物的氨溴加成反应情况, 其产物结构经核磁共振波谱及质谱分析确证, 并提出了可能的反应机理.     

Convenient one-pot synthesis of fluorinated DHPs derivatives and their further transformations

One-pot four-component reactions of aromatic aldehyde, Meldrum’s acid, ethyl-4,4,4-trifluoro-1,3-dioxobutanoate, and ammonium acetate afford ethyl 2-hydroxy-6-oxo-4-aryl-2-(trifluoromethyl)piperidine-3-carboxylate in good yields. The one-pot four-component process consists of an initial Michael addition, and a subsequent intramolecular cyclization. The effect of solvents on the reaction efficiency and yield is briefly investigated. The structure of product is further confirmed by XRD analysis. Meanwhile, the further transformation of hemi-aminal moiety to the corresponding dehydrated product is also achieved under the mild reaction conditions. The possible mechanism for the formation of product is presented.     

Microwave assisted rapid,catalyst-free,and efficient synthesis of a new class of diversely functionalized 3-hydroxy-2-oxindole scaffolds under aqueous reaction media

An efficient and rapid synthesis of a new class of diversely functionalized 3-substituted, 3-hydroxy-2-oxindoles scaffolds in catalyst-free conditions is described by the reaction of 1,3-diketone with isatins under microwave irradiation in aqueous medium. The generality of the reaction to afford the γ regioselective aldol addition products is well demonstrated by screening different structurally varied 1,3-diketone nucleophiles as well as isatin electrophiles. Simple reaction condition, good isolated yield of the product, and environmentally benign medium are attractive features of the present protocol.     

Synthesis of substituted 3-furan-2(5H)-ones via an anthracene Diels-Alder sequence

Deprotonation then electrophilic quench of the lactone derived from the Diels-Alder addition adduct of anthracene and maleic anhydride gave α-substituted lactones in good yield. Of particular note was the reaction with chlorotrimethylsilane which gave only the C-silylated product. Flash vacuum pyrolysis (FVP) of the alkylated products afforded 3-substituted furan-2(5H)-ones in good overall yield.     

Copper promoted C-S and C-N cross-coupling Reactions:The synthesis of 2-(N-Aryolamino)benzothiazoles and 2-(N-Aryolamino)benzimidazoles

The synthesis of 2-(N-aryolamino)benzothiazoles and 2-(N-aryolamino)benzimidazoles has been accomplished in the presence of copper catalyst. These reactions involve C-S and C-N cross-coupling reaction. All electron donating and withdrawing substituent's readily underwent the reaction to give target products in good to excellent yield. In addition, the reaction also gave target product in high yield with bulk scale.     

Proline-catalyzed asymmetric addition reaction of 9-tosyl-3,4-dihydro-beta-carboline with ketones

[reaction: see text] 9-Tosyl-3,4-dihydro-beta-carboline (1) reacted with a ketone in the presence of (S)-proline as a catalyst to give the corresponding addition product in good yield and high enantioselectivity. In the process, a small amount of water was found to affect the stereoselectivity of the products. The system was applied to reaction of compound 1 and 3-buten-2-one to give 3,4,6,7,12,12b-hexahydro-1H-indolo[2,3-a]quinolizin-2-one, which is a versatile precursor for the synthesis of some indole alkaloids.     

Palladium-catalyzed cross-coupling reaction of phenyl fluoroalkanesulfonates with organometallics

The palladium-catalyzed cross-coupling reaction of phenyl fluoroalkanesulfonates with organozinc, organotin and organoaluminum reagents in the presence of lithium chloride takes place to afford alkylbenzenes in good yields. However, the coupling reaction with organolithium and Grignard reagents proceeds unsatisfactorily with poor regioselectivity. On the basis of the isolation of an oxidative addition product of phenyl fluoroalkanesulfonate to palladium, a catalytic cycle in the reaction is suggested.     

在氯化亚锡存在下2,3-二甲基-2-丁烯与乙酐的催化酰化反应

一种新的催化剂,SnCl2·2H2O,已用于2,3-二甲基-2-丁烯与乙酐的酰化反应来制备高产率的3,3,4-三甲基-4-戊烯-2-酮 (TMP). 发现SnCl2·2H2O是室温下2,3-二甲基-2-丁烯与乙酐进行酰化反应的有效催化剂. 考察了催化剂用量、乙酐用量、反应时间和溶剂的加入等因素对该酰化反应的影响. 发现当催化剂/2,3-二甲基-2-丁烯摩尔比在0.30/1和 0.60/1之间、反应时间为2 h时,所得酰化产品的产率最高. 该酰化反应进行到完全所需的时间取决于催化剂用量和乙酐用量. 在需要加入溶剂的情况下,二氯甲烷或氯仿是一种合适的溶剂.     

Ene reaction of arynes with alkynes

Arynes, generated in situ from ortho-silylaryl triflates, undergo ene reaction with alkynes possessing propargylic hydrogen in the presence of KF/18-crown-6 in THF at room temperature to give substituted phenylallenes. Various terminal and internal alkynes as well as different arynes can be used to give the corresponding phenylallenes in good to moderate yields. The reaction of alkyne without propargylic hydrogen gave an acetylenic C-H addition product (a phenylalkyne) and a dehydro Diels-Alder product (a phenanthrene).     

Synthesis of silylallene glycosides and diene diglycosides by C-glycosidation of D-glucal with 1,4-bis(trimethylsilyl)-2-butyne

[reaction: see text] Silylmethylallenyl glycosides, symmetrical and unsymmetrical diene glycosides, were synthesized by C-glycosidation with 1,4-bis(trimethylsilyl)-2-butyne in good yield. The nature of the product is controlled by the choice of Lewis acid, BF(3).OEt(2), or SnCl(4). The efficient construction of unsymmetrical diene glycosides was achieved in one pot on the basis of the order of addition of sugar starting materials.     

Palladium‐Catalyzed Carbonylative Coupling of (2‐Azaaryl)methyl Anion Equivalents with (Hetero)Aryl Bromides

Conditions for the palladium‐catalyzed coupling of (2‐pyridyl)acetones with aryl bromides have been developed. Followed by an acid‐promoted deacetylation step, the desired 1‐(het)aryl‐2‐(2‐pyridyl)ethanones were obtained in good to excellent yields with high functional group tolerance. Test reactions revealed that both the addition of MgCl₂ and a specifically positioned heteroatom in the heteroaromatic ring were crucial for product formation indicating the importance of a chelated intermediate in the reaction mechanism. The reaction conditions proved suitable for a number of 5‐ and 6‐membered heteroaromatic starting materials affording all products in good yields. The utility of the obtained 1‐(het)aryl‐2‐(2‐pyridyl)ethanones was demonstrated by the straightforward synthesis of several multiaromatic derivatives in only few additional steps.     

Ligand-modulated stereo- and regioselective tandem addition reactions of rhenium-bound naphthalene

A series of complexes of the form TpRe(CO)(L)(eta(2)-naphthalene) (Tp = hydridotris(pyrazolyl)borate) undergoes tandem electrophile/nucleophile addition reactions with a high degree of regiocontrol depending on the auxiliary ligand, L. When L = PMe(3), the reaction of the eta(2)-naphthalene complex with triflic acid followed by a silyl ketene acetal favors the 1,4-addition product, whereas when L = pyridine, N,N-dimethylaminopyridine, N-methylimidazole, or NH(3) the 1,2-addition product is favored. These reactions proceed with excellent stereocontrol: both electrophile (H(+), D(+)) and nucleophile (silyl ketene acetal) add anti to the face of metal coordination, and a single coordination diastereomer can be isolated for each reaction. One-electron oxidation of the Re complex affords the corresponding free dihydronaphthalene in good yield.     

氧化铈对Pd／Al2O3表面上CO氧化性能的影响

采用ＴＰＤ－ＭＳ及ＴＰＳＲ－ＭＳ技术研究了添加ＣｅＯ２对Ｐｄ／Ａｌ２Ｏ３催化剂上ＣＯ脱附、表面反应及表面氧脱附等性能的影响，考察了不同含氧量的气氛下ＣＯ的氧化活性，结果表明，Ｐｄ－Ｃｅ间的相互作用有利于各自原子上表面氧的吸脱附及ＣＯ的表面反应，并发现ＣＯ２脱附量大小及峰温次序与对ＣＯ的催化氧化活性有一致的对应关系。     

C_（60）的胺加成反应和电喷雾电离质谱（ESI－MS）检测

报道了Ｃ６０与１，３－丙二胺和Ｎ，Ｎ－二甲基－１，３－丙二胺的加合反应，反应产物未经预先离子化处理直接用ＥＳＬ－ＭＳ进行检测。由于反应产物从甲苯溶液中析出，避免了生成多胺基加合物，产物以单加成物为主。当加合反应在空气氛下进行时，有加合氧的产物Ｃ６０Ｏｎ（ＮＨ２—ＣＨ２ＣＨ２ＣＨ２ＮＲ２）ｍ（Ｒ＝Ｈ，ＣＨ３）存在。实验发现：Ｎ，Ｎ－二甲基－１，３－丙二胺比１，３－丙二胺更容易与Ｃ６０发生多胺基加成和氧加成反应。通过控制反应条件可制备Ｃ６０二胺的单加成产物。