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61.
Sylvain Celanire Frederic Marlin Jack E. Baldwin Robert M. Adlington 《Tetrahedron》2005,61(12):3025-3032
The synthesis of 3,11-dioxatricyclo[5.3.1.01,5]undeca-5,9-dien-8-ones is reported from suitable 5-substituted furfuryl alcohols bearing an acetylenic side-chain. Successive peracid-mediated oxidative rearrangement of furan carbinols and base-assisted intramolecular 1,3-dipolar cycloaddition afforded oxygen-bridged tricyclo-undecane derivatives. Stereoselective transformations of cycloadducts are also discussed. 相似文献
62.
The reaction of electron-deficient cyclopropane derivatives, cis-1-methoxycarbonyl-2-aryl-6,6-dimethyl-5,7dioxospiro[2,5]octa-4,8-diones with benzoylmethylenetriphenylarsorane (2) and methoxycarbonylmethylenetriphenylarsorane (4) was found to form cis,trans-l-methoxycarbonyl-2-aryl-3-benzoyl-7,7-dimethyl-6,8-dioxospiro[3,5]nona-5,9-dione (3a-3e) and trans,cis,trans-5-[2‘-methoxycarbonyl-2‘-(triphenylarsoranylidene)acetyl]-6oxo-3-aryl-tetrahydro-pyran-2,4-dicarboxylic acid dimethyl esters (5a-5c) respectively with high stereoselectivity. The possible reaction mechanisms for the formation of the different products were also orooosed. 相似文献
63.
Jörg Rethmeier Andreas Rabenstein Monika Langer Ulrich Fischer 《Journal of chromatography. A》1997,760(2):637-302
Depending on the sulfur species, picomoles of different inorganic sulfur compounds can be detected and separated by HPLC in one arrangement in a sample volume less than 50 μl. The combination of fluorescence labelling of reduced inorganic sulfur compounds such as sulfide (S2−), sulfite(SO32− and thiosulfate (S2O32−) with monobromobimane followed by an extraction of elemental sulfur (S°) by chloroform treatment enables the detection of all mentioned sulfur compounds as well as sulfate (remaining aqueous phase) in the same sample. While the derivatized sulfur compounds could be detected by their fluorescence emission at 480 nm, elemental sulfur is identified by its UV absorption at 263 nm. Sulfate in the remaining aqueous phase is detected by HPLC with indirect UV detection at 254 nm. Detection ranges for the different sulfur compounds examined are as follows: sulfide (5 μM to 1.5 mM), sulfite (5 μM to 1.0 mM), thiosulfate (1 μM to 1.5 mM), elemental sulfur (2 μM to 32 mM) and sulfate (5 μM to >1 mM). 相似文献
64.
Man-Kit Lau Qian-Feng Zhang Wing-Tak Wong Wa-Hung Leung 《Journal of organometallic chemistry》2004,689(14):2401-2410
Treatment of [M(Buppy)2Cl]2 (M=Ir (1), Rh (2); BuppyH=2-(4′-tert-butylphenyl)pyridine) with Na(Et2NCS2), K[S2P(OMe)2], and K[N(Ph2PS)2]2 afforded monomeric [Ir(Buppy)2(S∧S)] (S∧S=Et2NCS2 (3), S2P(OMe)2 (4), N(PPh2S)2 (5)) and [Rh(Buppy)2(S∧S)] (S∧S=Et2NCS2 (6), S2P(OMe)2 (7), N(PPh2S)2 (8)), respectively. Reaction of 1 with Na[N(PPh2Se)2] gave [Ir(Buppy)2{N(PPh2Se)2}] (9). The crystal structures of 3, 4, 7, and 8 have been determined. Treatment of 1 or 2 with AgOTf (OTf=triflate) followed by reaction with KSCN gave dinuclear [{M(Buppy)2}2(μ-SCN)2] (M=Ir (10), Rh (11)), in which the SCN− ligands bind to the two metal centers in a μ-S,N fashion. Interaction of 1 and 2 with [Et4N]2[WQ4] gave trinuclear heterometallic complexes [{Ir(Buppy)2}2(μ-WQ4)] (Q=S (12), Se (13)) and [{Rh(Buppy)2}2{(μ-WQ)4}] (Q=S (14), Se (15)), respectively. Hydrolysis of 12 led to formation of [{Ir(Buppy)2}2{W(O)(μ-S)2(μ3-S)}] (16) that has been characterized by X-ray diffraction. 相似文献
65.
Rongyi Zhang Qigang Li Dr. Qiqiang Xie Prof. Dr. Chuanfa Ni Prof. Dr. Jinbo Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(71):17773-17779
The ring-opening difluoromethylation-halogenation of cyclic (thio)ethers is reported through a simple strategy relying on carbon-chalcogen bond activation with difluorocarbene. The reaction proceeds through in situ protonation of the previously little-known difluoromethylene oxonium or sulfonium ylide intermediate followed by ring-opening with halide ion to afford halogenated acyclic difluoromethyl (thio)ethers that can then be employed for further elaboration. TMSCF2X (X=Br, Cl) are unique reagents to achieve this synthetic purpose, which serve as both the difluorocarbene source and the halide ion source. 相似文献
66.
Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo‐heterocycles 下载免费PDF全文
María Inés Flores‐Conde Fabiola N. de la Cruz Julio López J. Óscar C. Jiménez‐Halla Eduardo Peña‐Cabrera Marcos Flores‐Álamo Francisco Delgado Miguel A. Vázquez 《应用有机金属化学》2018,32(3)
The unprecedented reaction of ketone‐containing aromatic pyridinium salts 3a ‐ e and alkynyl Fischer complexes 1a ‐ f proceeds via a mild domino process to provide 4,6‐disubstituted pyran‐2‐ones 5a ‐ k and 2,3,5‐trisubstituted furans 6a ‐ h (45‐97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products. 相似文献
67.
Tandem reaction of α-diazocarbonyl compounds in the presence of rhodium(II) acetate catalyst is described to furnish a range of conformationally restricted C2 symmetric macrodiolides via head to tail dimerization of intramolecular carbonyl ylides. 相似文献
68.
The cheap and easily available sodium dithionite and thiourea dioxide have been used as the source of sulfonyl group in the synthesis of sulfones and sulfonamides recently.Compared with other methods for the sulfonylation reactions,the strategies using sodium dithionite or thiourea dioxide provide an alternative and complementary route to diverse sulfonyl compounds.During the reaction process,sulfur dioxide anion radical is the key intermediate,which is usually generated from a single electron transfer under suitable conditions.The advantages using sodium dithionite or thiourea dioxide in the sulfonylation reactions include mild conditions and broad substrate scope with excellent functional group compatibility.Further applications by using sodium dithionite and thiourea dioxide in organic transformations will be anticipated. 相似文献
69.
Malek Taher Maghsoodlou Nourollah Hazeri Sayyed Mostafa Habibi Khorasani Aqil Ghulame Shahzadeh Mahmoud Nassiri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):913-919
Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong NH acids, such as indole and 2-methyl indole, 3-methyl indole, and 5-boromo indole. These stable ylides exist in a solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group. 相似文献
70.
Ali Ramazani Ebrahim Ahmadi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):565-567
Magnesium hydrogen sulfate powder was found to catalyze stereoselective conversion of dialkyl 2-(imido-N-yl)-3-(triphenylphosphorany-lidene)butanedioates to electron-poor (Z)-N-vinylimides in solvent-free conditions at 95°C 1 h in high conversions. Microwave also was found to catalyze the same reactions in the presence of magnesium hydrogen sulfate powder in solvent-free conditions in 3 min. 相似文献