- Phospha-Michael addition reaction of maleimides employing N-heterocyclic phosphine-thiourea as a phosphonylation reagent: synthesis of 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonate derivatives
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N-Heterocyclic phosphine (NHP)-thiourea as a novel phosphonylation reagent has been successfully applied for the phospha-Michael reaction of maleimides under catalyst and additive free reaction conditions. This methodology enables desymmetrization of a variety of maleimide derivatives to provide 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonates in up to 92% yield. Synthetic manipulation of this Michael adduct afforded an ethylphosphonate and a phosphino lactam. Furthermore, a scale-up experiment for its practical usage as a versatile precursor in organic synthesis was readily demonstrated.
- Molleti, Nagaraju,Bjornberg, Chad,Kang, Jun Yong
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Read Online
- N,O-ditosylethanolamine as effective reagent for the synthesis of heterocyclic tertiary amine salts
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During the synthesis of N-tosylaziridine, two unexpected products were isolated: 1-(2-(p-tolylsulfonamido)ethyl)pyridinium p-tolylsulfonate (3) and N,N,O-tri-(p-tolylsulfonyl)ethanolamine (3a). The structures of 3 and 3a were investigated in solid state b
- Cherepakhin, Valeriy S.,Zaitsev, Kirill V.,Churakov, Andrei V.,Oprunenko, Yuri F.,Zaitseva, Galina S.,Karlov, Sergey S.
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- Titanium(IV) Complexes Based on Tridentate N,N,O Ligands - Synthesis, Structure, and Thermal Decomposition
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New tridentate N,N,O-type ligands MeN(CH2CH2NHTs)(CH2CR2OH) [Ts = tosyl; R = H, 6, (N,N,OH)H2; R = Ph, 7 (N,N,OPh)H2] were prepared. The corresponding diisopropoxide c
- Cherepakhin, Valeriy S.,Zaitsev, Kirill V.,Oprunenko, Yuri F.,Churakov, Andrei V.,Lermontova, Elmira Kh.,Zaitseva, Galina S.,Karlov, Sergey S.
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Read Online
- Syntheses and crystal structures of Ni(II) complexes with pyridine-based macrocyclic ligands
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Three pyridine-based macrocyclic ligands, two containing one pyridine pendant arm (L1 and L2) and one containing piperazine rings in the macrocyclic scaffold (L3), with an increasing size of the macrocycle from 12-, 14- to 30-membered ring for L1–L3 were synthesized and characterized. A series of Ni(II) complexes with all these ligands, with molecular formulas [NiL1(CH3OH)](ClO4)2 (1), [NiL2(CH3CN)](ClO4)2 (2), and [Ni2L3(DMF)2(CH3CN)2](ClO4)4 (3) (DMF = N,N–dimethylformamide), was prepared and thoroughly characterized. Single crystal X-ray structural analysis confirmed that all the complexes have a coordination number of six and their geometries are close to octahedral. In the case of the mononuclear complexes 1 and 2, all the nitrogen atoms of the macrocycle are coordinated, however, in the dinuclear complex 3 with the piperazine-based ligand L3, two nitrogen donor atoms (of the total number of ten) are uncoordinated. The first coordination spheres of all the complexes are completed by solvent molecules. The values of effective magnetic moments, determined by the Evans method in solution, are 3.12, 3.19 and 4.36 μB for complexes 1, 2 and 3, respectively, which correspond well to the theoretical spin-only values.
- Císa?ová, Ivana,Draho?, Bohuslav,Zahradníková, Eva
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supporting information
(2021/11/17)
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- Complexes and Ligands
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The present application provides ligands and fluorescent or luminescent complexes comprising these ligands.
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- Bright and stable luminescent probes for target engagement profiling in live cells
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The pace of progress in biomedical research directly depends on techniques that enable the quantitative interrogation of interactions between proteins and other biopolymers, or with their small-molecule ligands. Time-resolved F?rster resonance energy transfer (TR-FRET) assay platforms offer high sensitivity and specificity. However, the paucity of accessible and biocompatible luminescent lanthanide complexes, which are essential reagents for TR-FRET-based approaches, and their poor cellular permeability have limited broader adaptation of TR-FRET beyond homogeneous and extracellular assay applications. Here, we report the development of CoraFluors, a new class of macrotricyclic terbium complexes, which are synthetically readily accessible, stable in biological media and exhibit photophysical and physicochemical properties that are desirable for biological studies. We validate the performance of CoraFluors in cell-free systems, identify cell-permeable analogs and demonstrate their utility in the quantitative domain-selective characterization of Keap1 ligands, as well as in isoform-selective target engagement profiling of HDAC1 inhibitors in live cells. [Figure not available: see fulltext.]
- Payne, N. Connor,Kalyakina, Alena S.,Singh, Kritika,Tye, Mark A.,Mazitschek, Ralph
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p. 1168 - 1177
(2021/10/25)
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- Diastereoselective Desymmetrization of p-Quinamines through Regioselective Ring Opening of Epoxides and Aziridines
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A highly diastereoselective desymmetrization of p-quinamines via regioselective ring opening of epoxides and aziridines under mild conditions has been developed. A chairlike six-membered transition state with minimized 1,3-diaxial interactions explains the relative stereoselectivity of the cyclization reaction. This transition-metal free [3 + 3] annulation reaction provides rapid access to fused bicyclic morpholines and piperazines with a tetrasubstituted carbon center in high yields. In addition, it also allows the synthesis of enantioenriched products by using easily accessible chiral nonracemic epoxides and aziridines.
- Jadhav, Sandip B.,Chegondi, Rambabu
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supporting information
p. 10115 - 10119
(2019/12/24)
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- Identifying new lead structures to enhance tolerance towards drought stress via high-throughput screening giving crops a quantum of solace
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Novel synthetic lead structures interacting with RCAR/(PYR/PYL) receptor proteins were identified based on the results of a high-throughput screening campaign of a large compound library followed by focused SAR studies of the three most promising hit clusters. Whilst indolinylmethyl sulfonamides 8y,z and phenylsulfonyl ethylenediamines 9y,z showed strong affinities for RCAR/ (PYR/PYL) receptor proteins in wheat, thiotriazolyl acetamides 7f,s exhibited promising efficacy against drought stress in vivo (wheat, corn and canola) combined with confirmed target interaction in wheat and arabidopsis thaliana. Remarkably, binding affinities of several representatives of 8 and 9 were on the same level or even better than the essential plant hormone abscisic acid (ABA).
- Frackenpohl, Jens,Schneider, Linn,Decker, Luka J.B.,Dittgen, Jan,Fenkl, Franz,Fischer, Christian,Franke, Jana,Freigang, Joerg,Getachew, Rahel,Gonzalez Fernandez-Nino, Susana M.,Helmke, Hendrik,Hills, Martin J.,Hohmann, Sabine,Kleemann, Jochen,Kurowski, Karoline,Lange, Gudrun,Luemmen, Peter,Meyering, Nicole,Poree, Fabien,Schmutzler, Dirk,Wrede, Sebastian
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- Synthesis of indolines: Via a palladium/norbornene-catalyzed reaction of aziridines with aryl iodides
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A Pd- and norbornene-catalyzed domino procedure has been developed to synthesize indoline compounds. This reaction provides efficient access to indolines by employing aryl iodides with aziridines as new electrophiles. The transformation is scalable and tolerates a range of functional groups.
- Liu, Ce,Liang, Yujie,Zheng, Nian,Zhang, Bo-Sheng,Feng, Yuan,Bi, Siwei,Liang, Yong-Min
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supporting information
p. 3407 - 3410
(2018/04/05)
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- Novel methinic functionalized and dendritic C-scorpionates
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The study of chelating ligands is undoubtedly one of the most significant fields of research in chemistry. The present work is directed to the synthesis of new functionalized derivatives of tripodal C-scorpionate compounds. Tris-2,2,2-(1-pyrazolyl)ethanol, HOCH2C(pz)3 (1), one of the most important derivatives of hydrotris(pyrazolyl)methane, was used as a building block for the synthesis of new functionalized C-scorpionates, aiming to expand the scope of this unexplored class of compounds. The first dendritic C-scorpionate was successfully prepared and used in the important industrial catalytic reactions, Sonogashira and Heck C-C cross-couplings.
- Martins, Luísa M.D.R.S.,Wanke, Riccardo,Silva, Telma F.S.,Pombeiro, Armando J.L.,Servin, Paul,Laurent, Régis,Caminade, Anne-Marie
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supporting information
(2018/11/30)
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- Modular One-Step Three-Component Synthesis of Tetrahydroisoquinolines Using a Catellani Strategy
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Reported is a modular one-step three-component synthesis of tetrahydroisoquinolines using a Catellani strategy. This process exploits aziridines as the alkylating reagents, through palladium/norbornene cooperative catalysis, to enable a Catellani/Heck/aza-Michael addition cascade. This mild, chemoselective, and scalable protocol has broad substrate scope (43 examples, up to 90 % yield). The most striking feature of this protocol is the excellent regioselectivity and diastereoselectivity observed for 2-alkyl- and 2-aryl-substituted aziridines to access 1,3-cis-substituted and 1,4-cis-substituted tetrahydroisoquinolines, respectively. Moreover, this is a versatile process with high step and atom economy.
- Qian, Guangyin,Bai, Miao,Gao, Shijun,Chen, Han,Zhou, Siwei,Cheng, Hong-Gang,Yan, Wei,Zhou, Qianghui
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supporting information
p. 10980 - 10984
(2018/07/30)
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- Dual Gold-Catalyzed Formal Tetradehydro-Diels–Alder Reactions for the Synthesis of Carbazoles and Indolines
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This work reports a dual gold-catalyzed tetradehydro-Diels–Alder reaction for the synthesis of nitrogen-containing aromatic heterocycles. Under the catalytic system (IPrAuNTf2/DIPEA), indolines and carbazoles as well as other N-containing aromatic heterocycles were prepared in high yields with good functional group tolerance. Unlike the traditional thermal tetradehydro-Diels–Alder reactions, diluted reaction concentration and radical prohibitors are not required for this protocol. Experimental data support a mechanism involving gold vinylidene species, which undergoes a 6 π electrocyclization, followed with 1,2-hydrogen shift.
- Wang, Hong-Fa,Wang, Shi-Yue,Qin, Tian-Zhu,Zi, Weiwei
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supporting information
p. 17911 - 17914
(2018/11/23)
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- Direct spirocyclization from keto-sulfonamides: An approach to azaspiro compounds
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Spontaneous spirocyclization of keto-sulfonamides via ynamides through a one-pot process is presented. Push-pull ynamides were obtained through Michael addition/elimination without Cu. The obtained azaspiro compounds are building blocks for indole alkaloids. Theoretical studies provide insights into the mechanism of the formal Conia-ene reaction.
- Beltran, Frédéric,Fabre, Indira,Ciofini, Ilaria,Miesch, Laurence
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supporting information
p. 5042 - 5045
(2017/11/06)
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- Triiodide-Mediated δ-Amination of Secondary C?H Bonds
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The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)-mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2-mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide-mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates.
- Wappes, Ethan A.,Fosu, Stacy C.,Chopko, Trevor C.,Nagib, David A.
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supporting information
p. 9974 - 9978
(2016/08/16)
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- N-protected 1,2-oxazetidines as a source of electrophilic oxygen: Straightforward access to benzomorpholines and related heterocycles by using a reactive tether
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A hitherto unknown reactivity of a strained four-membered heterocycle, 1,2-oxazetidine, is reported. When reacted with organometallic compounds, this reagent provides electrophilic oxygen with a nitrogen-terminated two-carbon-atom tether. The synthetic versatility of the products obtained was demonstrated in various transformations, leading to efficient synthesis of six-, seven-, and eight-membered heterocyclic systems of pharmaceutical importance. Open and then close: The O-selective ring-opening reaction of 1,2-oxazetidines with organometallic compounds provides tethered phenol derivatives that can be used to access six-, seven-, and eight-membered heterocyclic systems in only a few steps (see scheme; Ts=tosyl).
- Javorskis, Tomas,Sriubaite, Simona,Bagd?iunas, Gintautas,Orentas, Edvinas
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p. 9157 - 9164
(2015/06/16)
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- Mild regiospecific synthesis of 1-alkoxy-isochromenes catalyzed by well-defined [silver(I)(pyridine-containing ligand)] complexes
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The synthesis of 3-substituted-1-alkoxyisochromenes starting from 2-alkynylbenzaldehydes and different alcohols is reported. The reaction is catalyzed by a silver(I) complex with an original macrocyclic pyridine-containing ligand. The approach is characterized by absolute regioselectivity, mild reaction conditions, good to excellent reaction yields, cleanness of the reaction, and reduced purification steps. The reaction mechanism was investigated by in-depth 1H NMR experiments and an aimed trapping experiment.
- Dellacqua, Monica,Castano, Brunilde,Cecchini, Clara,Pedrazzini, Tommaso,Pirovano, Valentina,Rossi, Elisabetta,Caselli, Alessandro,Abbiati, Giorgio
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p. 3494 - 3505
(2014/05/06)
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- Fluoroalkanosulfonyl fluorides-mediated cyclodehydration of β-hydroxy sulfonamides and β-hydroxy thioamides to the corresponding aziridines and thiazolines
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An efficient method for the fluoroalkanosulfonyl fluoride-induced cyclodehydration of β-hydroxy sulfonamides and β-hydroxy thioamides to the corresponding aziridines and thiazolines is reported. Mild reaction conditions, operational simplicity, and high y
- Yan, Zhaohua,Guan, Chengbo,Yu, Zhangxin,Tian, Weisheng
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supporting information
p. 5788 - 5790
(2013/10/01)
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- Catalytic asymmetric alkylation reactions for the construction of protected ethylene-amino and propylene-amino motifs attached to quaternary stereocentres
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An efficient catalytic and stereoselective method for the direct construction of protected ethylene-amino and propylene-amino scaffolds attached to quaternary stereocentres is reported. Preliminary investigations revealed a mild base catalysed nucleophilic ring opening of N-sulfonyl aziridines using the commercially available phosphazene base 2-tert-butylimino-2-diethylamino-1,3- dimethyl-perhydro-1,3,2-diazaphosphorine (BEMP) was possible and resulted in highly efficient alkylation reactions with a range of methine carbon acids. This reaction could be rendered highly asymmetric (up to 97 % ee) by employing phase-transfer catalysis to control stereoinduction. Incorporation of alkyl substituents onto the aziridine electrophile, resulted in a highly diastereoselective (up to 30:1 d.r.) variant of this methodology. A further extension using N-protected cyclic sulfamidates as the electrophilic component was successful with a range of pro-nucleophiles (up to 96 % ee and 45:1 d.r.) and allowed a range of nitrogen protecting groups (carbamate, sulfonyl, phosphonyl, benzyl) to be incorporated into the alkylation adducts. Finally, the utility of the products have been demonstrated in the synthesis of useful heterocycles and compounds bearing structural components of natural products. Open sesame: The enantio- and diastereoselective nucleophilic ring opening of protected aziridines and cyclic sulfamidates using asymmetric phase-transfer catalysis (PTC) is reported. The ring-opening alkylation reactions create quaternary chiral centres containing ethylene- and propylene-amino motifs in good yields with good to excellent enantioselectivities (see scheme). These reactions are broad in scope and a wide range of pro-nucleophiles are tolerated. Copyright
- Moss, Thomas A.,Barber, David M.,Kyle, Andrew F.,Dixon, Darren J.
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supporting information
p. 3071 - 3081
(2013/03/28)
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- Lithiation-electrophilic trapping of N-sulfonyl-activated ethylene aziridines
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A detailed study on the lithiation-electrophilic trapping of N-sulfonyl ethylene aziridines is described. The optimum results required use of a N-2,4,6-tri-iso-propylbenzenesulfonyl activating group and lithiation using 3 equiv. of s-BuLi-PMDETA for 1 min
- Huang, Jianhui,Moore, Stephen P.,O'Brien, Peter,Whitwood, Adrian C.,Gilday, John
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supporting information; experimental part
p. 335 - 345
(2009/03/11)
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- Investigation of macrocyclisation routes to 1,4,7-triazacyclononanes: Efficient syntheses from 1,2-ditosylamides
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Two routes to the synthesis of a cyclohexyl-fused 1,4,7-triazacyclononane involving macrocyclisations of tosamides have been investigated. In the first approach, using a classic Richman-Atkins-type cyclisation of a cyclohexyl-substituted 1,4,7-tritosamide
- Stones, Graham,Tripoli, Regis,McDavid, Colin L.,Roux-Duplgtre, Kewin,Kennedy, Alan R.,Sherrington, David C.,Gibson, Colin L.
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p. 374 - 384
(2008/10/09)
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- LUMINESCENT MACROCYCLIC LANTHANIDE COMPLEXES
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The present invention provides a novel class of macrocyclic compounds as well as complexes formed between a metal (e.g., lanthanide) ion and the compounds of the invention. Preferred complexes exhibit high stability as well as high quantum yields of lanthanide ion luminescence in aqueous media without the need for secondary activating agents. Preferred compounds incorporate hydroxy-isophthalamide moieties within their macrocyclic structure and are characterized by surprisingly low, non-specific binding to a variety of polypeptides such as antibodies and proteins as well as high kinetic stability. These characteristics distinguish them from known, open-structured ligands.
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Page/Page column 77
(2008/12/05)
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- Total syntheses of tambjamines C, E, F, G, H, i and J, BE-18591, and a related alkaloid from the marine bacterium pseudoalteromonas tunicata
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The acetate salts of tambjamines C, E, and F (2-4, respectively), as well as those of the related alkaloids BE-18591 (5) and 6, have been prepared by treatment of bipyrrole aldehyde 16 with the relevant amine in the presence of acetic acid. The 5′-bromc-a
- Pinkerton, David M.,Banwell, Martin G.,Willis, Anthony C.
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p. 5127 - 5130
(2008/03/28)
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- Novel preparation of functionalized iodotetrahydronaphthyridine, iodoazaindoline, and iodotetrahydropyridoazepine systems
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A novel method, which utilizes a key halogen dance step for the preparation of iodotetrahydronaphthyridine, iodoazaindoline, and iodotetrahydropyridoazepine ring-systems is described. A variety of transformations of the iodo-functional group are also repo
- Nguyen, Hanh Nho,Wang, Zhan J.
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p. 7460 - 7463
(2008/03/14)
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- The use of vinyl sulfonium salts in the stereo-controlled asymmetric synthesis of epoxide- and aziridine-fused heterocycles: Application to the synthesis of (-)-balanol
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(Chemical Equation Presented) Lift your ylides: An asymmetric, epoxy-annulation reaction mediated by a vinyl sulfonium salt converts aminoaldehydes and -ketones into fused heterocyclic epoxides. The methodology was extended to an aziridine-annulation reac
- Unthank, Matthew G.,Hussain, Nigel,Aggarwal, Varinder K.
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p. 7066 - 7069
(2007/10/03)
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- 2-(1,3,5-Dithiazinan-5-yl)ethanol heterocycles, structure and reactivity
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Treatment of 2-(1,3,5-dithiazinan-5-yl)ethanol (1), 2-(1,3,5-dithiazinan-5- yl)-1-phenylethanol (2), 2-(1,3,5-dithiazinan-5-yl)-1-methylethanol (3) and 2-(1,3,5-dithiazinan-5-yl)-2-methyl-1-phenylethanol (4) with TsCl and NEt 3 in CH2Cl2 afforded the corresponding 3-tosyl-1,3-oxazolidine derivatives (5-8), whereas tosylation of 1-4 in the presence of NHMe3Cl gave the corresponding O-tosyl-2-(1,3,5- dithiazinan-5-yl)ethanol derivatives (11-14). The direct preparation of 5 and 7 from formaldehyde and N-tosylethanolamine (9) or N-tosyl-2-propanolamine was not successful. Reactions of 1 or 3 with benzylamine furnish 1,3,5-tribenzyl-1,3,5- triazinane. Heating of 1 and 2 affords the corresponding 1,3,5-tri(2- hydroxyethyl)-1,3,5-triazinanes. X-Ray diffraction studies of compounds (1-9 and 11) are reported.
- Gálvez-Ruiz, Juan Carlos,Jaen-Gaspar, Javier C.,Castellanos-Arzola, Indira G.,Contreras, Rosalinda,Flores-Parra, Angelina
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p. 2269 - 2285
(2007/10/03)
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- A new method for the preparation of nitrogen-containingheterocycles using diphenylsulfonium triflates
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Various nitrogen heterocycles were produced by the reactions of ω-bromoalkyldiphenylsulfonium or diphenylsyylsulfonium triflates with nitrogen nucleophiles. Further, the reactions of diphenylstyrylsulfonium triflates with N-metalated phthalimide and imida
- Yamanaka, Hiroyuki,Yamane, Yoshinobu,Mukaiyama, Teruaki
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p. 2813 - 2826
(2007/10/03)
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- Angular ligand constraint yields an improved olefin aziridination catalyst
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(Matrix presented) The use of a pyridinophane, a macrocycle composed of three pyridines linked, via all ortho positions through CH2 or CH2CH2 groups, bound to copper, gives good performance (rate and yield) catalyzing the
- Vedernikov, Andrei N.,Caulton, Kenneth G.
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p. 2591 - 2594
(2007/10/03)
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- Preparation of hexaaza and heptaaza macrocycles functionalized with a single aminoalkyl pendant arm
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A practical and reproducible route for the preparation of 1,4,7,10,13,16,19-heptaazacyclohenicosane (1), 1,4,7,10,13,16-hexaazacyclooctadecane (2), and 1,4,7,10,13,17-hexaazacycloicosane (3) bearing a single N-(2-amino-ethyl) pendant arm has been develope
- Zhang, Zhibo,Mikkola, Satu,Loennberg, Harri
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p. 854 - 858
(2007/10/03)
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- Short and efficient synthesis of optically active N-tosyl aziridines from 2-amino alcohols
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Two alternative and complementary one-pot procedures for the direct transformation of 2-amino alcohols to N-tosyl aziridines are presented. The unsubstituted parent compound and its less hindered homologues can be obtained in high yields by tosylation and
- Bieber, Lothar W.,De Araujo, Maria C. F.
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p. 902 - 906
(2007/10/03)
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- Design of a neutral macrocyclic ionophore: Synthesis and binding properties for nitrate and bromide anions
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A macrocyclic neutral ionophore 8 (X = O) capable of binding weakly coordinating anions such as nitrate and bromide in DMSO solution has been designed by a stepwise, deductive approach. The optimum geometrical arrangement of the hydrogen bond donor sites
- Herges, Rainer,Dikmans, Anton,Jana, Umasish,Koehler, Felix,Jones, Peter G.,Dix, Ina,Fricke, Tom,Koenig, Burkhard
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p. 3004 - 3014
(2007/10/03)
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- Selective synthesis of heterocyclic compounds through the intramolecular substitution of phenylselenonyl group by nitrogen or carbonyl oxygen in amides
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Nitrogen heterocycles were produced by the oxidation of N-[ω-(phenylseleno)alkyl]-p-toluenesulfonamides through the intramolecular substitution of the resultant phenylselenonyl group by the nitrogen atom. By the oxidation of the corresponding benzamides,
- Toshimitsu,Hirosawa,Tanimoto,Uemura
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p. 4017 - 4020
(2007/10/02)
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- Substituted thienylethylamines and process for their production
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Substituted thienylethylamines of the formula: STR1 wherein R is formyl, acetyl or benzoyl or is benzyl, which is ring-substituted by at least one halogen atom, and R1 is a lower alkyl, phenyl or substituted phenyl, are initial products for the production of antithrombolytically effective pharmaceutical agents. A process for the production of the above-mentioned compounds from substituted ethanolamines by their reaction with strong bases, further reaction with the resultant aziridines with 2-thienyllithium, and conversion of the resultant thienylethylamines with compounds of formula RX, wherein R has the above-mentioned meaning and X is a halogen.
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- RING-CLOSURE REACTIONS. XXV. WHY ARE STRAINED SMALL RINGS SO EASILY FORMED IN INTRAMOLECULAR NUCLEOPHILIC SUBSTITUTION REACTIONS?
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The leaving group effect (kBr/kCl) has been determined for two typical series of SN2 cyclisation reactions in the ring size range of 3 to 6 in order to probe the effect of ring strain on transition state structure.The general increase of the magnitude of the leaving group effect on going from the less strained to the more strained ring systems indicates that bond making and bond breaking is significant also in the small ring transition states.The apparent unimportance of strain in the products to the ease of closure of the smallest rings is tentatively explained by the hypothesis that the adverse effect of ring strain is partially offset by a significant reduction of non-bonded interactions in the transition states.
- Casadei, Maria Antonietta,Martino, Alessandro di,Galli, Carlo,Mandolini, Luigi
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p. 659 - 664
(2007/10/02)
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- Nuclear Magnetic Resonance as a Means of Assessing Structure versus Reactivity Relationships in Alicyclic Compounds
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Proton-carbon-13 coupling constants (J13C,H) have been measured for three series of N-substituted azacycloalkanes.Structural features of the alicyclic compounds, as revealed by this and other n.m.r.techniques, reflect the strain present in the ring and can be used as a guide to predict ring-closure reactivity.Deviations from such structure versus reactivity relationships are found with highly strained small rings.Hence, it must be stressed that meaningful trends in the behaviour of ring compounds can only be revealed when large homologous series are examined.Literature X-ray structural studies are also exploited in order to comment on the situation in small rings and on their peculiar ring-closure tendency.It is suggested that, although some of the experimental features and behaviour can be accounted for in terms of strain, others, in the case of three-membered rings, are to be attributed to the presence of ?-aromaticity.Because of this, these three-membered ring compounds can efficiently gain stabilization by resonance interaction with exocyclic conjugative substituents: n.m.r. evidence is given on this point.
- Cerichelli, Giorgio,Galli, Carlo,Lillocci, Claudio,Luchetti, Luciana
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p. 725 - 728
(2007/10/02)
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- Heterocyclic β-Enamino Esters, 38 - Comparative Investigations on Heterocyclic β-Enamino Nitriles. Synthesis of Heterocondensed Pyrimidines
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β-Enamino nitriles of the furan- (1a - e), thiophene- (2), and pyrrole series (3) are obtained from malonodinitrile and oxiranes, thiirane, and N-tosylaziridine in the presence of bases; depending on the reaction conditions in the latter case (1:2)- (pyrr
- Wamhoff, Heinrich,Thiemig, Heinz-Albrecht
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p. 4473 - 4485
(2007/10/02)
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- SYNTHESIS OF THE NEW BIS-AZAMACROCYCLE 1,2-BIS(1,4,8,12-TETRAAZACYCLOTETRADECANYL)ETHANE AND OF ITS DICOPPER(II) COMPLEX
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The sinthesis and characterisation of the new bis-azamacrocycle 1,2-bis(1,4,8,12-tetraazacyclotetradecanyl)ethane and its dicopper(II) complex are reported.The sinthetic route proposed is relatively easy and versatile and can be applied to produce diffren
- Garcia-Espana, Enrique,Micheloni, Mauro,Paoletti, Piero,Bianchi, Antonio
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p. 399 - 400
(2007/10/02)
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- Synthesis of Macrobicyclic Polyamides by Direct Macrobicyclisation via Tripode-Tripode Coupling
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The synthesis of five macrobicyclic polyamides 1-5 is described following a route in which the macrobicycle is formed by the coupling of two tripodal subunits.Such a sequence is appreciably shorter than the stepwise construction via a macrocycle, and may
- Dietrich, Bernard,Hosseini, Mir Wais,Lehn, Jean-Marie,Sessions, Richard B.
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p. 289 - 299
(2007/10/02)
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- Ring-closure Reactions. Part 23. Kinetics of Formation of Three- to Seven-membered-ring N-Tosylazacycloalkanes. The Role of Ring Strain in Small- and Common-sized-ring Formation
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Rates of cyclisation of a series of anions derived from N-tosyl-ω-bromoalkylamines to nitrogen heterocycles with three to seven members in Me2SO-H2O (99:1) have been studied.Rates vary markedly with ring size in the order 5 > 3 > 6 > 7 ca. 4.First order rate constants for cyclisation have been translated into effective molarities (EM) with reference to an appropriate intermolecular model reaction.Comparison of the present results with available literature data on SN2 ring-closure reactions leading to small- and common-sized rings reveals that the ease of formation of three-membered rings is much more structure-dependent than that of the higher homologues.This remarkable behaviour is believed to parallel the unique way in which the stability of three-membered rings is affected by structure.As a rule, the ease of cyclisation appears to bear an inverted relationship to the assumed strain energy of the ring product.The apparent opposition of this rule to earlier conclusions in the literature is discussed.
- Martino, Alessandro Di,Galli, Carlo,Gargano, Patrizia,Mandolini, Luigi
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p. 1345 - 1350
(2007/10/02)
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- SYNTHESIS OF CHIRAL DIAZA-CROWN ETHERS INCORPORATING CARBOHYDRATE UNITS
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A synthesis of a novel chiral diaza crown ethers derived from α-D-glucose, α-D-mannose, and α-D-galactose in two alternative pathways is described.
- Pietraszkiewicz, M.,Jurczak, J.
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p. 2967 - 2970
(2007/10/02)
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- Synthesis of Selectively Protected Tri- and Hexaamine Macrocycles
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A general route to tri- and hexaamine macrocycles containing selectively protected diethylenetriamine units has been developed.Condensation of the N'-benzoyl-N,N"-bis(p-tolylsulfonyl)diethylenetriamine N,N"-disodium salt with bissulfonate esters of two-, four-, and six-carbon diols at high reactant concentrations gave the corresponding 9- and 18- (85percent and 1percent), 11- and 22- (30percent and 20percent), and 13- and 26- (56percent and 17percent) membered tri- and hexaamine macrocycles, respectively.The benzoyl group was selectively removed with potassium tert-butoxide in ca. 90percent yield, and the macrocycles were conveniently separated by chromatography.Details of the synthetic procedures and characterization of the new selectively protected tri- and hexaamine macrocycles are described.
- Martin, Andrea E.,Ford, Thomas M.,Bulkowski, John E.
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p. 412 - 415
(2007/10/02)
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- Dianions of glyoxylic acid thioketals: convenient α-keto acid equivalents
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By varying the solvent, reaction temperature, and bases (i.e., gegenions present), optimum conditions for the alkylation of the dianions of glyoxylic acid derivatives 8 and 9 were established.It was found, that the easily prepared, thermally stable, tetrahydrofuran-soluble potassium dianion of bis(ethylthio)acetic acid was readily alkylated by alkyl halides, tosylates, epoxides, and N-tosyl aziridines.The latter alkylation is being used to develop a possible cytochalasin synthesis.The alkylated products may be readily converted into the corresponding α-keto acids or methyl 2,2-bismethoxycarboxylates.
- Bates, Gordon S.,Ramaswamy, S.
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p. 716 - 722
(2007/10/02)
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