24401-36-3Relevant articles and documents
syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
supporting information, p. 3604 - 3612 (2021/07/26)
Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
Highly Enantioselective Catalytic Kinetic Resolution of α-Branched Aldehydes through Formal Cycloaddition with Homophthalic Anhydrides
Farid, Umar,Aiello, Maria Luisa,Connon, Stephen J.
, p. 10074 - 10079 (2019/07/18)
A new catalytic methodology was developed to promote an efficient one-pot kinetic resolution of racemic aldehydes with selectivity (s*) of up to 91 (99:1 d.r., >99 % ee) in a cycloaddition reaction with enolizable anhydrides to afford dihydroisocoumarin products (a core prevalent in natural products and molecules of medicinal interest) containing three contiguous stereocentres.
Pyrolysis of azetidinone derivatives: A versatile route towards electron-rich alkenes, C-1 allylation and/or homologation of aldehydes
Al-Hamdan, Nouf S.,Habib, Osama M.,Ibrahim, Yehia A.,Al-Awadi, Nouria A.,El-Dusouqui, Osman M. E.
, p. 21023 - 21031 (2014/06/09)
Pyrolysis of β-lactams and β-thiolactams led essentially to stereoselective synthesis of the high energy electron-rich Z-alkenes. Extension of this methodology to the pyrolysis of 3-allyloxy derivatives gave a simple direct route to the synthetically important 4-pentenal. These pyrolytic transformations convert aldehydes to aryloxyalkenes (a protected homologation) and 4-pentenal (a C-1 allylation and homologation). The starting 3-aryloxy and 3-allyloxy-β-lactams were synthesized by the standard Staudinger ketene-imine [2 + 2] cycloaddition. The corresponding β-thiolactams have readily been obtained in good yields by thiation of β-lactams with Lawesson's reagent. This journal is the Partner Organisations 2014.
Palladium/Bronsted acid-catalyzed α-allylation of aldehydes with allylic alcohols
Jiang, Gaoxi,List, Benjamin
experimental part, p. 1667 - 1670 (2011/09/14)
A simple, highly efficient, and readily scalable direct α-allylation of aldehydes with allylic alcohols that is co-catalyzed by palladium and a Bronsted acid has been developed. Copyright
C-N bond cleavage of allylic amines via hydrogen bond activation with alcohol solvents in Pd-catalyzed allylic alkylation of carbonyl compounds
Zhao, Xiaohu,Liu, Delong,Guo, Hui,Liu, Yangang,Zhang, Wanbin
supporting information; experimental part, p. 19354 - 19357 (2012/01/06)
Hydrogen-bond-activated C-N bond cleavage of allylic amines was realized in Pd-catalyzed allylic alkylation to form the C-C bond product. The method could be expanded to a series of allylic amines and carbonyl compounds with excellent results. It provides a new and convenient access to C-C bond formation based on Pd-catalyzed allylic alkylation of allylic amines by using only inexpensive alcohol solvents.
Diastereoselective access to trans -2-substituted cyclopentylamines
Joosten, Antoine,Lambert, Emilie,Vasse, Jean-Luc,Szymoniak, Jan
supporting information; experimental part, p. 5128 - 5131 (2011/01/05)
A highly diastereoselective synthesis of trans-2-substituted cyclopentylamines via a tandem hydrozirconation/Lewis acid-mediated cyclization sequence applied to butenyl oxazolidines is described. The method allows an easy preparation of diversely substituted cyclopentylamines which appear to be useful synthetic intermediates. This was further illustrated by the syntheses of (±)-Rodocaine, (±)-trans-pentacin, and enantiomerically enriched trans-cyclopentane-1,2-diamine.
Multi-product classes obtained from allylation of α-halo ketones with allylzinc bromide
Zhang, Min,Hu, Yuanyuan,Zhang, Songlin
supporting information; experimental part, p. 10732 - 10735 (2010/04/05)
An efficient, one-pot synthesis procedure for the preparation of allylic epoxides, aldehydes and homoallylic alcohols (see scheme) has been described. The three industrial products were synthesized by the reaction of allylzinc bromide with a-halo ketones
Microwave-assisted generation of alkoxyl radicals and their use in additions, β-fragmentations, and remote functionalizations
Hartung, Jens,Daniel, Kristina,Gottwald, Thomas,Gross, Andreas,Schneiders, Nina
, p. 2313 - 2322 (2008/02/08)
Microwave irradiation (2.45 GHz, 300-500 W) of N-(alkoxy)thiazole-2(3H)- thiones in low-absorbing solvents affords alkoxyl radicals, which were identified by (i) spin adduct formation (EPR-spectroscopy) and (ii) fingerprint-type selectivities in intramolecular additions (stereoselective synthesis of disubstituted tetrahydrofurans), β-fragmentations (formation of carbonyl compounds), and C,H-activation of aliphatic subunits, by δ-selective hydrogen atom transfer. C-Radicals formed from oxygen-centered intermediates were trapped either by Bu3SnH, l-cysteine ethyl ester, the reduced form of glutathione (reductive trapping), or by bromine atom donor BrCCl3 (heteroatom functionalization) The results suggest that microwave activation is superior to UV/Vis-photolysis and conductive heating for alkoxyl radical generation from N-(alkoxy)thiazolethiones. It offers by far the shortest reaction times along with the option to reduce the amount of trapping reagent significantly. The Royal Society of Chemistry 2006.
Palladium-catalyzed synthesis of N-aryl pyrrolidines from γ-(N-arylamino) alkenes: Evidence for chemoselective alkene insertion into Pd-N bonds
Ney, Joshua E.,Wolfe, John P.
, p. 3605 - 3608 (2007/10/03)
The formation of a C-C and a C-N bond in a reaction between γ-(N-arylamino) alkenes and aryl bromides results in the stereoselective synthesis of substituted pyrrolidine derivatives (see scheme). Preliminary studies suggest these reactions proceed by intramolecular alkene insertion into the Pd-N bond of intermediate [Pd(Ar)(amido)] complexes. dba = dibenzylideneacetone, dppb = 1,3-bis(diphenylphosphanyl) butane.
Non-carbonyl-stabilized metallocarbenoids in synthesis: The development of a tandem rhodium-catalyzed bamford-stevens/thermal aliphatic claisen rearrangement sequence
May, Jeremy A.,Stoltz, Brian M.
, p. 12426 - 12427 (2007/10/03)
A tandem rhodium-catalyzed Bamford-Stevens/Claisen rearrangement is presented. The tandem reaction uses Eschenmoser hydrazones for the in situ generation of non-carbonyl-stabilized diazo alkanes, which are presumably intercepted by Rh(II) catalysts to induce a 1,2-hydride migration. This sequence provides high levels of stereocontrol for the generation of simple acyclic (Z)-enol ethers. These enol ethers undergo either thermal or Lewis acid accelerated Claisen rearrangements to provide products of high diastereopurity. Also presented are cascade reactions, wherein a third chemical step occurs after the initial tandem sequence (i.e., Bamford-Stevens/Claisen/ene and Bamford-Stevens/Claisen/Cope). Copyright
