7796-73-8Relevant academic research and scientific papers
Extended Hydrogen Bond Networks for Effective Proton-Coupled Electron Transfer (PCET) Reactions: The Unexpected Role of Thiophenol and Its Acidic Channel in Photocatalytic Hydroamidations
Berg, Nele,Bergwinkl, Sebastian,Nuernberger, Patrick,Horinek, Dominik,Gschwind, Ruth M.
supporting information, p. 724 - 735 (2021/02/01)
Preorganization and aggregation in photoredox catalysis can significantly affect reactivities or selectivities but are often neglected in synthetic and mechanistic studies, since the averaging effect of flexible ensembles can effectively hide the key activation signatures. In addition, aggregation effects are often overlooked due to highly diluted samples used in many UV studies. One prominent example is Knowles's acceleration effect of thiophenol in proton-coupled electron transfer mediated hydroamidations, for which mainly radical properties were discussed. Here, cooperative reactivity enhancements of thiophenol/disulfide mixtures reveal the importance of H-bond networks. For the first time an in-depth NMR spectroscopic aggregation and H-bond analysis of donor and acceptor combined with MD simulations was performed revealing that thiophenol acts also as an acid. The formed phosphate-H+-phosphate dimers provide an extended H-bond network with amides allowing a productive regeneration of the photocatalyst to become effective. The radical and acidic properties of PhSH were substituted by Ph2S2 and phosphoric acid. This provides a handle for optimization of radical and ionic channels and yields accelerations up to 1 order of magnitude under synthetic conditions. Reaction profiles with different light intensities unveil photogenerated amidyl radical reservoirs lasting over minutes, substantiating the positive effect of the H-bond network prior to radical cyclization. We expect the presented concepts of effective activation via H-bond networks and the reactivity improvement via the separation of ionic and radical channels to be generally applicable in photoredox catalysis. In addition, this study shows that control of aggregates and ensembles will be a key to future photocatalysis.
Synthesis of 5-[(Pentafluorosulfanyl)methyl]-γ-butyrolactones via a Silver-Promoted Intramolecular Cyclization Reaction
Roudias, Majdouline,Gilbert, Audrey,Paquin, Jean-Fran?ois
, p. 6655 - 6665 (2019/11/03)
The synthesis of 5-[(pentafluorosulfanyl)methyl]-γ-butyrolactones bearing different substituents at position 3 or 4 is reported. A silver-promoted intramolecular cyclization of substituted 4-chloro-5-(pentafluorosulfanyl)pentanoic acids allows the preparation of the substituted SF5-containing γ-butyrolactones in up to 96 % yield.
Pheromone synthesis. Part 264: Synthesis of the core 3-oxabicyclo[3.3.0]octane structures of gomadalactones A, B and C, the components of the contact sex pheromone of the white-spotted longicorn beetle, Anoplophora malasiaca
Mori, Kenji
, p. 3387 - 3398 (2019/05/15)
The core bicyclic cyclopentanelactone structures of gomadalactones A, B and C with α-hydroxyketone system were synthesized from (R)-pulegone, employing deconjugation of an α,β-unsaturated lactone as the key step. Comparison of the CD spectra of the synthetic compounds with those of the natural products confirmed the absolute configuration of the natural pheromone components as proposed in 2007. X-ray crystallographic analysis of the model compound of gomadalactone B core structure was carried out.
C(alkenyl)-H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis
Liu, Mingyu,Yang, Pusu,Karunananda, Malkanthi K.,Wang, Yanyan,Liu, Peng,Engle, Keary M.
supporting information, p. 5805 - 5813 (2018/05/14)
A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO2 as the stoichiometric oxidant or co-catalytic Co(OAc)2 and O2 (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.
Rapid Access to Thiolactone Derivatives through Radical-Mediated Acyl Thiol-Ene and Acyl Thiol-Yne Cyclization
McCourt, Ruairi O.,Dénès, Fabrice,Sanchez-Sanz, Goar,Scanlan, Eoin M.
supporting information, p. 2948 - 2951 (2018/05/28)
A new synthetic approach to thiolactones that employs an efficient acyl thiol-ene (ATE) or acyl thiol-yne (ATY) cyclization to convert unsaturated thiocarboxylic acid derivatives into thiolactones under very mild conditions is described. The high overall yields, fast kinetics, high diastereoselectivity, excellent regiocontrol, and broad substrate scope of these reaction processes render this a very useful approach for diversity-oriented synthesis and drug discovery efforts. A detailed computational rationale is provided for the observed regiocontrol.
Direct oxidative lactonization of alkenoic acids mediated solely by NaIO4: Beyond a simple oxidant
Kang, Yan-Biao,Chen, Xian-Min,Yao, Chuan-Zhi,Ning, Xiao-Shan
supporting information, p. 6193 - 6196 (2016/05/19)
Triflic acid-catalyzed direct oxidative lactonization of alkenoic acids mediated solely by NaIO4 without halogen salts is described. Sodium periodate works not only as an oxidant, but also as an active reagent and directly mediates the lactonization. A new cheap, green, and practical oxidative lactonization approach has been developed using NaIO4 as the sole reagent.
Enantioselective Synthesis of (+)-Peganumine A
Piemontesi, Cyril,Wang, Qian,Zhu, Jieping
, p. 11148 - 11151 (2016/10/11)
A gram-scale enantioselective total synthesis of (+)-peganumine A was accomplished in 7 steps from commercially available 6-methoxytryptamine. Key steps included (a) a Liebeskind-Srogl cross-coupling; (b) a one-pot construction of the tetracyclic skeleton from an ω-isocyano-γ-oxo-aldehyde via a sequence of an unprecedented C-C bond forming lactamization and a transannular condensation; (c) a one-pot organocatalytic process merging two achiral building blocks into an octacyclic structure via a sequence of enantioselective Pictet-Spengler reaction followed by a transannular cyclization. This last reaction created two spirocycles and a 2,7-diazabicyclo[2.2.1]heptan-3-one unit with excellent control of both the absolute and relative stereochemistry of the two newly created quaternary stereocenters.
Gold I-catalyzed highly diastereo- and enantioselective alkyne oxidation/cyclopropanation of 1,6-enynes
Qian, Deyun,Hu, Haoxiang,Liu, Feng,Tang, Bin,Ye, Weimin,Wang, Yidong,Zhang, Junliang
supporting information, p. 13751 - 13755 (2015/02/19)
A highly enantioselective oxidative cyclo-propanation of 1,6-enynes catalyzed by cationic AuI/ chiral phophoramidite complexes is presented. The new method provides convenient access to densely functionalized bicyclo[3.1.0]hexanes bearing three contiguous quaternary and tertiary stereogenic centers with high enantioselectivity (up to e.r. 98:2). Control experiments suggest that the quinoline moiety of the b-gold vinyloxyquinolinium intermediate in the reaction plays an important role in promoting good enantiose-lectivity through a transitional auxiliary effect in the transition state.
Sodium dithionite initiated reaction of pent-4-en-1-amines with fluoroalkyl iodides for the synthesis of 2-fluoroalkyl pyrrolidine derivatives
Zhu, Yaoping,Yeng, Xueyan,Fang, Xiang,Yang, Xianjin,Ye, Lingling,Cai, Wei,Zhang, Yan,Wu, Fanhong
experimental part, p. 1251 - 1257 (2011/04/16)
Pent-4-en-1-amines are reactive to fluoroalkyl iodides with respect to sodium dithionite initiated free radical addition reactions. We report here the development of a novel and efficient synthesis of 2-fluoroalkyl pyrrolidine derivatives by sodium dithio
Acyloxylactonisations mediated by lead tetracarboxylates
Cottrell, Ian F.,Cowley, Andrew R.,Croft, Laura J.,Hymns, Lauren,Moloney, Mark G.,Nettleton, Ewan J.,Kirsty Smithies,Thompson, Amber L.
supporting information; experimental part, p. 2537 - 2550 (2009/08/07)
The reaction of lead(IV) tetracarboxylates with carboxylic acids containing unsaturated side chains has been found to give acyloxy lactone products in a diastereoselective process; the reaction can be extended to lead(IV) tetrazolates to give the analogous outcome. Mechanistic implications of these results are discussed.
