Pawel Dziedzic
Stockholm University
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Publication
Featured researches published by Pawel Dziedzic.
Journal of Physical Chemistry A | 2009
Barbara Nozière; Pawel Dziedzic
Glyoxal, a common atmospheric gas, has been reported to be depleted in some regions of the atmosphere. The corresponding sink could be accounted for by reactions in or at the surface of atmospheric particles, but these reactions were not identified. Recently, we showed that inorganic ammonium ions, NH(4)(+), are efficient catalysts for reactions of carbonyl compounds, including glyoxal, in the liquid phase. To determine whether ammonium-catalyzed reactions can contribute to depletion of glyoxal in the atmosphere, the reactivity of this compound in aqueous solutions containing ammonium salts (ammonium sulfate, chloride, fluoride, and phosphate) at 298 K has been studied. The products identified by LC-HRMS and UV absorption revealed a mechanism involving two distinct pathways: a Bronsted acid pathway and an iminium pathway. The kinetics of the iminium pathway was studied by monitoring formation of a specific product. This pathway was second order in glyoxal in most of the solutions studied and should therefore be second order in most ammonium-containing aerosols in the atmosphere. The corresponding rate constant, k(II) (M(-1) s(-1)), increased strongly with ammonium ion activity, a(NH(4)(+)), and pH: k(II) (M(-1) s(-1)) = (2 +/- 1) x 10(-10) exp((1.5 +/- 0.8)aNH(4)(+)) exp((2.5 +/- 0.2)pH). This iminium pathway is a lower limit for the ammonium-catalyzed consumption of glyoxal, but the contribution of the acid pathway is expected to be small in tropospheric aerosols. With these results the reactive uptake of glyoxal on ammonium-containing aerosols was estimated and shown to be a possible explanation for depletion of this compound in Mexico City.
Chemistry: A European Journal | 2008
Ismail Ibrahem; Gui-Ling Zhao; Ramon Rios; Jan Vesely; Henrik Sundén; Pawel Dziedzic
The development of one-pot organocatalytic domino Michael/alpha-alkylation reactions between bromomalonates or bromoacetoacetate esters and alpha,beta-unsaturated aldehydes is presented. The chiral-amine-catalyzed reactions with bromomalonates as substrates give access to the corresponding 2-formylcyclopropane derivatives in high yields with excellent diastereoselectivity and up to 99 % ee. The catalytic domino Michael/alpha-alkylation reactions between 4-bromo-acetoacetate and enals provide a route for the synthesis of functionalized cyclopentanones in good to high yields with 93-99 % ee. The products from the organocatalytic reactions were also reduced with high diastereoselectivity to the corresponding cyclopropanols and cyclopentanols, respectively. Moreover, one-pot combinations of amine and heterocyclic carbene catalysis (AHCC) enabled the highly enantioselective synthesis of beta-malonate esters (91-97 % ee) from the reaction between bromomalonates and enals. The tandem catalysis included the catalytic domino reaction followed by catalytic in situ chemoselective ring-opening of the 2-formylcyclopropane intermediates.
Chemistry: A European Journal | 2010
Gui-Ling Zhao; Farman Ullah; Luca Deiana; Shuangzheng Lin; Qiong Zhang; Junliang Sun; Ismail Ibrahem; Pawel Dziedzic
The first examples of one-pot highly chemo- and enantioselective dynamic kinetic asymmetric transformations (DYKATs) involving alpha,beta-unsaturated aldehydes and propargylated carbon acids are presented. These DYKATs, which proceed by a combination of catalytic iminium activation, enamine activation, and Pd(0)-catalyzed enyne cycloisomerization, give access to functionalized cyclopentenes with up to 99 % ee and can be used for the generation of all-carbon quaternary stereocenters.
Geophysical Research Letters | 2007
Barbara Nozière; Pawel Dziedzic
Secondary Organic Aerosols (SOA), produced by the transformation of organic gases in the atmosphere, have received a considerable amount of attention over the last three decades because of their ex ...
Chemistry: A European Journal | 2009
Farman Ullah; Gui-Ling Zhao; Luca Deiana; Mingzhao Zhu; Pawel Dziedzic; Ismail Ibrahem; Peter Hammar; Junliang Sun
A highly chemo- and enantioselective organocatalytic addition of fluorocarbon nucleophiles, such as 1-fluoro-bis(phenylsulfonyl)methane, toα,β-unsaturated aldehydes is presented (see scheme). The reactions are catalyzed by simple chiral amines and give access to optically active fluorine derivatives in good yields and up to 95 % ee. Notably, the methodology can be applied to the formation of a chiral quaternary carbon center bearing a fluorine atom with high enantioselectivity.
Chemistry: A European Journal | 2011
Luca Deiana; Pawel Dziedzic; Gui-Ling Zhao; Jan Vesely; Ismail Ibrahem; Ramon Rios; Junliang Sun
The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99% ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and up to 99% ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99% ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocyclic carbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92-99%. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.
Chemistry: A European Journal | 2011
Samson Afewerki; Palle Breistein; Kristian Pirttilä; Luca Deiana; Pawel Dziedzic; Ismail Ibrahem
Branching out! The first co-catalytic enantioselective (up to 98:2 e.r.) β-alkylation of α,β-unsaturated aldehydes by combination of simple chiral amine and copper catalysts provides β-branched aldehydes in a one-pot protocol. The methodology was applied to the short total syntheses of bisabolane sesquiterpenes (S)-(+)-curcumene, (E)-(S)-(+)-3-dehydrocurcumene and (S)-(+)-tumerone.
Chemistry: A European Journal | 2009
Pawel Dziedzic; Patric Schyman; Martin Kullberg
Easily side-tracked: A simple route to the paclitaxel side chain and its analogues is based on the (R)-proline-catalyzed addition of aldehydes to N-(phenylmethylene)benzamides, followed by oxidation of the resulting protected alpha-hydroxy-beta-benzoylaminoaldehydes (92-99 % ee). Esterification of the subsequent phenylisoserine derivatives with baccatin III gives paclitaxel analogues (see scheme).A simple highly enantioselective organocatalytic addition of aldehydes to N-(phenylmethylene)benzamides is presented. The application of (R)-proline as the catalyst and subsequent oxidation of the protected alpha-hydroxy-beta-benzoylaminoaldehydes (92-99 % ee) gives access to esterification-ready phenylisoserine derivatives such as the protected paclitaxel (taxol) side chain. Esterification of these derivatives with baccatin III gives access to the cancer chemotherapeutic substance paclitaxel and its analogues that do not exist in nature.
Chemistry: A European Journal | 2008
Gui-Ling Zhao; Ismail Ibrahem; Pawel Dziedzic; Junliang Sun; Charlotte Bonneau
A highly enantioselective organocatalytic one-pot synthesis of nitro-, formyl-, and ester-functionalized cyclopentanes with four stereocenters is presented. The cyclopentanes were formed as a predominant diasteroisomer and isolated in high yields with 97-99 % ee.
Chemical Communications | 2005
Weibiao Zou; Ismail Ibrahem; Pawel Dziedzic; Henrik Sundén
Simple peptides and their analogues having a primary amino group as the catalytic residue mediate the direct asymmetric intermolecular aldol reaction with high stereoselectivity and furnish the corresponding aldol products with up to 99% ee; this intrinsic ability of highly modular peptides may explain the initial molecular evolution of aldolase enzymes.