Center for Molecular Modeling - S. Stankovic

Anomalous cyclic conjugation in benzenoid molecules with a small number of Kekule structures

wim — Tue, 09 Apr 2013 14:09:51 +0000

I. Gutman, S. Stankovic, R. Kovacevic, J. Durdevic, B. Furtula

Indian Journal of Chemistry Section A

44 (9), 1751-1755

2013

Published while none of the authors were employed at the CMM

DOI

http://dx.doi.org/

A difference between the pi-electron properties of catafusenes and perifusenes

wim — Tue, 09 Apr 2013 13:52:26 +0000

S. Gojak, S. Radenkovic, R. Kovacevic, S. Stankovic, J. Durdevic, I. Gutman

Polycyclic Aromatic Compounds

26 (3), 197-206

2007

Published while none of the authors were employed at the CMM

DOI

http://dx.doi.org/10.1080/10406630600760568

On the cycle-dependence of topological resonance energy

wim — Tue, 09 Apr 2013 13:51:06 +0000

I. Gutman, S. Stankovic, J. Durdevic, B. Furtula

Journal of Chemical Information and Modeling (JCIM)

47 (3), 776-781

2007

Published while none of the authors were employed at the CMM

DOI

http://dx.doi.org/10.1021/ci6004977

Partitioning of pi-electrons in rings of diaza-derivatives of acenes

wim — Tue, 09 Apr 2013 13:47:29 +0000

S. Stankovic, J. Durdevic, I. Gutman, R. Milentijevic

Journal of the Serbian Chemical Society

73 (5), 547-554

2008

Published while none of the authors were employed at the CMM

DOI

http://dx.doi.org/10.2298/JSC0805547S

Solvent-controlled selective transformation of 2-Bromomethyl-2-methylaziridines to functionalized aziridines and azetidines

michel — Sun, 18 Dec 2011 20:34:45 +0000

S. Stankovic, H. Goossens, S. Catak, M. Tezcan, M. Waroquier, V. Van Speybroeck, M. D'Hooghe, N. De Kimpe

Journal of Organic Chemistry

77, 3181-3190

2012

Abstract

The reactivity of 2-bromomethyl-2-methylaziridines toward oxygen, sulfur, and carbon nucleophiles in different solvent systems was investigated. Remarkably, the choice of the solvent has a profound influence on the reaction outcome, enabling the selective formation of either functionalized aziridines in dimethylformamide (through direct bromide displacement) or azetidines in acetonitrile (through rearrangement via a bicyclic aziridinium intermediate). In addition, the experimentally observed solvent-dependent behavior of 2-bromomethyl-2-methylaziridines was further supported by means of DFT calculations.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1021/jo202637a

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12 j.org_.chem 77, 3181 Stankovic.pdf

Systematic Study of Halide-Induced Ring Opening of 2-Substituted Aziridinium Salts and Theoretical Rationalization of the Reaction Pathways

wim — Tue, 13 Sep 2011 12:11:31 +0000

M. D'Hooghe, S. Catak, S. Stankovic, M. Waroquier, Y. Kim, H-J. Ha, V. Van Speybroeck, N. De Kimpe

European Journal of Organic Chemistry

25, 4920-4931

2010

Abstract

The ring-opening reactions of 2-alkyl-substituted 1,1-bis(arylmethyl)- and 1-methyl-1-(1-phenylethyl)aziridinium salts with fluoride, chloride, bromide and iodide in acetonitrile have been evaluated for the first time in a systematic way. The reactions with fluoride afforded regioisomeric mixtures of primary and secondary fluorides, whereas secondary β-chloro, β-bromo and β-iodo amines were obtained as the sole reaction products from the corresponding halides by regiospecific ring opening at the substituted position. Both experimental and computational results revealed that the reaction outcomes in the cases of chloride, bromide and iodide were dictated by product stability through thermodynamic control involving rearrangement of the initially formed primary halides to the more stable secondary halides. The ring opening of the same aziridinium salts with fluoride, however, was shown to be mediated by steric interactions (kinetic control), with the corresponding primary β-fluoro amines being obtained as the main reaction products. Only for 2-acylaziridinium ions was the reaction outcome shown to be under full substrate control, affording secondary β-fluoro, β-chloro, β-bromo and β-iodo amines through exclusive attack at the activated α-carbonyl carbon atom.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1002/ejoc.201000486

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10 Eur. J. of Org. Chem. 4920-4931 dhooghe.pdf

Synthesis of 3-Methoxyazetidines via an Aziridine to Azetidine Rearrangement and Theoretical Rationalization of the Reaction Mechanism

wim — Mon, 22 Aug 2011 14:38:15 +0000

S. Stankovic, S. Catak, M. D'Hooghe, H. Goossens, K. Abbaspour Tehrani, P. Bogaert, M. Waroquier, V. Van Speybroeck, N. De Kimpe

Journal of Organic Chemistry

76 (7), 2157-2167

2011

Abstract

The synthetic utility of N-alkylidene-(2,3-dibromo-2-methylpropyl)amines and N-(2,3-dibromo-2-methylpropylidene)benzylamines was demonstrated by the unexpected synthesis of 3-methoxy-3-methylazetidines upon treatment with sodium borohydride in methanol under reflux through a rare aziridine to azetidine rearrangement. These findings stand in contrast to the known reactivity of the closely related N-alkylidene-(2,3-dibromopropyl)amines, which are easily converted into 2-(bromomethyl)aziridines under the same reaction conditions. A thorough insight into the reaction mechanism was provided by both experimental study and theoretical rationalization.

DOI

http://dx.doi.org/10.1021/jo102555r

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11 j. org. chem. 76,2157 stankovic.pdf

Regioselectivity in the ring opening of non-activated aziridines

wim — Mon, 22 Aug 2011 14:00:39 +0000

S. Stankovic, M. D'Hooghe, S. Catak, M. Waroquier, V. Van Speybroeck, N. De Kimpe, H-J. Ha

Chemical Society Reviews

41, 643-665

2012

Abstract

In this critical review, the ring opening of non-activated 2-substituted aziridines via intermediate aziridinium salts will be dealt with. Emphasis will be put on the relationship between the observed regioselectivity and inherent structural features such as the nature of the C2 aziridine substituent and the nature of the electrophile and the nucleophile. This overview should allow chemists to gain insight into the factors governing the regioselectivity in aziridinium ring openings (81 references).

DOI

http://dx.doi.org/10.1039/C1CS15140A

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12 Chem. Soc. Rev.41 643 Stancovic.pdf.pdf

Reactivity of Activated versus Nonactivated 2-(Bromomethyl)aziridines with respect to Sodium Methoxide: a Combined Computational and Experimental Study

wim — Mon, 22 Aug 2011 13:30:29 +0000

H. Goossens, K. Vervisch, S. Catak, S. Stankovic, M. D'Hooghe, F. De Proft, P. Geerlings, N. De Kimpe, M. Waroquier, V. Van Speybroeck

Journal of Organic Chemistry

76 (21), 8698-8709

2011

Abstract

The difference in reactivity between the activated 2-bromomethyl-1-tosylaziridine and the non-activated 1-benzyl-2-(bromomethyl)aziridine with respect to sodium methoxide was analyzed by means of DFT calculations within the supermolecule approach, taking into account explicit solvent molecules. In addition, the reactivity of epibromohydrin with regard to sodium methoxide was assessed as well. The barriers for direct displacement of bromide by methoxide in methanol are comparable for all three heterocyclic species under study. However, ring opening was found to be only feasible for the epoxide and the activated aziridine, and not for the non-activated aziridine. According to these computational analyses, the synthesis of chiral 2-substituted 1-tosylaziridines can take place with inversion (through ring opening/ring closure) or retention (through direct bromide displacement) of configuration upon treatment of the corresponding 2-(bromomethyl)aziridines with one equivalent of a nucleophile, whereas chiral 2-substituted 1-benzylaziridines are selectively obtained with retention of configuration (via direct bromide displacement). Furthermore, the computational results showed that explicit accounting for solvent molecules is required to describe the free energy profile correctly. To verify the computational findings experimentally, chiral 1-benzyl-2-(bromomethyl)aziridines and 2-bromomethyl-1-tosylaziridines were treated with sodium methoxide in methanol. The presented work concerning the reactivity of 2-bromomethyl-1-tosylaziridine stands in contrast to the behaviour of the corresponding 1-tosyl-2-(tosyloxymethyl)aziridine with respect to nucleophiles, which undergoes a clean ring-opening/ring-closure process with inversion of configuration at the asymmetric aziridine carbon atom.

DOI

http://dx.doi.org/10.1021/jo201255z

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11 j. org. chem. 76,8698 goossens.pdf

DFT calculations on Aziridines within the supermolecule approach

lore — Tue, 12 Feb 2013 08:45:37 +0000

H. Goossens, S. Catak, S. Stankovic, M. D'Hooghe, N. De Kimpe, M. Waroquier, V. Van Speybroeck

Poster

Conference / event / venue

MolSim-2013

Amsterdam, The Netherlands

Monday, 7 January, 2013 to Friday, 18 January, 2013

Conference reference

Molsim-2013