S. Mangelinckx

Diastereoselective aldol reaction of zincated 3-chloro-3-methyl-1- azaallylic anions as key-step in the synthesis of 1,2,3,4- tetrasubstituted 3-chloroazetidines

S. Mangelinckx, B. De Sterck, F. Colpaert, S. Catak, J. Jacobs, S. Rooryck, M. Waroquier, V. Van Speybroeck, N. De Kimpe
Journal of Organic Chemistry
77 (7), 3415–3425
2012
A1

Abstract 

Zincated 3-chloro-3-methyl-1-azaallylic anions undergo a stereoselective aldol addition across aromatic aldehydes and subsequent mesylation to produce syn alpha-chloro-beta-mesyloxyketimines, which were isolated in 80-84% yield and high diastereomeric excess (dr > 97/3) after purification via flash chromatography. The syn alpha-chloro-beta-mesyloxyketimines were further stereoselectively reduced to give stereochemically defined 3-aminopropyl mesylates, which were cyclized to 1,2,3,4-tetrasubstituted 3-chloroazetidines containing three contiguous stereogenic centers. DFT calculations on the key aldol addition revealed the presence of a highly ordered bimetallic six-membered twist-boat-like transition state structure with a tetra-coordinated metal cyclic structure. DFT calculations revealed that chelation of both zinc and lithium cations in the transition state structure leads to the experimentally observed high syn diastereoselectivity of aldol reactions.

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A theoretical study on the solvated structural properties of various metalated 3-halo-1-azaallylic anions

B. De Sterck, V. Van Speybroeck, S. Mangelinckx, G. Verniest, N. De Kimpe, M. Waroquier
Journal of Physical Chemistry A
113 (22), 6375-6380
2009
A1

Abstract 

Metalated 3-halo-1-azaallylic anions are important building blocks for the preparation of a wide variety of heterocyclic and highly functionalized compounds. A theoretical description of the structural properties of halogenated 1-azaallylic anions in vacuo and in tetrahydrofuran (THF) solution is presented to gain insight into their reactivity behavior. The configurational flexibility of fluorinated and chlorinated 1-azaallylic anions is examined, and it is shown that these anions have far less configurational flexibility as compared with nonhalogenated analogues, with a strong preference to occur as Z/anti isomers. In addition, the driving force for transmetalation, that is, the replacement of the lithium cations with K+, Cu+, ZnCl+, CuCl+, or MgBr+ is studied. To obtain reliable results, the structures were modeled in THF using the combined implicit/explicit solvent approach resulting in different coordination numbers for lithium in the Z/anti and E/anti isomers. Calculations on dimerization energies show that coordination with THF is energetically preferred over aggregation.

Experimental and Computational Study of the Conrotatory Ring Opening of Various 3-Chloro-2-azetines

S. Mangelinckx, V. Van Speybroeck, P. Vansteenkiste, M. Waroquier, N. De Kimpe
Journal of Organic Chemistry
73 (14) 5481-5488
2008
A1

Abstract 

A combined experimental and theoretical study is presented on 2-azetines, a class of azaheterocyclic compounds, which are difficult to access but have shown a unique reactivity as strained cyclic enamines. New highly substituted 2-azetines bearing aryl substituents at the 2- and 4-position were synthesized from 3,3-dichloroazetidines. Whereas 2-aryl-3,3-dichloroazetidines gave stable 2-aryl-3-chloro-2-azetines upon treatment with sodium hydride in DMSO, 2,4-diaryl-3,3-dichloroazetidines showed a remarkably different reactivity in that they afforded benzimidoyl-substituted alkynes under similar mild treatment with base. The formation of the alkynes involves electrocyclic ring opening of intermediate 2,4-diaryl-3-chloro-2-azetines and elimination of hydrogen chloride. Ab initio theoretical calculations confirmed the experimental findings and demonstrated that the 4-aryl substituent is responsible for this remarkably enhanced reactivity of 2-azetines toward electrocyclic conrotatory ring opening by a significant decrease in reaction barrier of about 30 kJ/mol. This activation effect by an aryl group in the allylic position toward electrocyclic ring opening of unsaturated four-membered rings is of general importance since a similar increased reactivity of 4-aryloxetes, 4-arylthiete-1,1-dioxides, and 3-arylcyclobutenes has been reported in literature as well.

Reaction of Electrophilic Allyl Halides with Amines: A Reinvestigation

S. Mangelinckx, D. Courtheyn, R. Verhe, V. Van Speybroeck, M. Waroquier, N. De Kimpe
Synthesis-Stuttgart
(13), 2260-2264
2006
A1

Abstract 

The Michael-induced ring closure (MIRC) of amines with 2-bromoalkylidenemalonates has been reinvestigated and the reaction products with primary amines have been identified as (2-iminoethyl)malonates and not 2-aminoalkylidenemalonates as previously reported. The (2-iminoethyl)malonates are formed by ring opening of the intermediate unstable 2-aminocyclopropane-1,1-dicarboxylates (beta-ACCs) and were characterized spectroscopically and via chemical transformation.

Insight into the solvation and isomerization of 3-halo-1-azaallylic anions from ab initio metadynamics calculations and NMR experiments

R. Declerck, B. De Sterck, T. Verstraelen, G. Verniest, S. Mangelinckx, J. Jacobs, N. De Kimpe, M. Waroquier, V. Van Speybroeck
Chemistry - A European Journal
15 (3), 580 - 584
2009
A1

Abstract 

Long live theZisomer! The solvation and isomerization properties of lithiated 3-chloro-1-azaallylic anions in tetrahydrofuran are revealed. Extensive and convincing evidence is obtained from state-of-the-art first-principle molecular dynamics and metadynamics simulations in an explicit periodic solvent model, together with detailed NMR experiments.

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