Regio‐ and stereoselectivity of [2 + 3] cycloaddition of (E)‐β‐nitrostyrenes to (Z)‐C,N‐diphenylnitrone in the light of AM1 and AM1/COSMO calculations

Barański, A.; Olszanska, Marta; Barańska, Katarzyna

doi:10.1002/1099-1395(200009)13:9<489::aid-poc267>3.3.co;2-z

Cited by 2 publications

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“…Cycloadditions of nitrones were the subject of intensive theoretical studies; however, the vast majority of them dealt with alkenes 27,31-37 or alkynes 27,31 as dipolarophiles. These works include investigations of the reaction mechanism, ,,,, the effects of Lewis acids (e.g., BH 3 , BF 3 ) 33,34 and solvents 27b,34-36 on the mechanism and reaction energetic parameters, and the nature of the regio- and stereoselectivity. 27b,31a,32d,− At the same time, 1,3-DCA to nitriles was studied theoretically toward azides, ,, and especially nitrile oxides 7g or nitrones 7f but only in a few publications.…”

Section: Resultsmentioning

confidence: 99%

Theoretical Study of Reactant Activation in 1,3-Dipolar Cycloadditions of Cyclic Nitrones to Free and Pt-Bound Nitriles

Kuznetsov

Kukushkin

2005

J. Org. Chem.

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[reaction: see text] 1,3-Dipolar cycloaddition of the cyclic nitrones CH2(CH2)2CH=NO (N1), CH2CH2OCH=NO (N2), CH2-OCH2CH=NO (N3), and O(CH2)2CH=NO (N4) to organonitriles, RCN-both free (R = CH(3), CF(3)) and ligated to Pt(II) and Pt(IV) (in the complexes trans-[PtCl(2)(NCCH(3))(2)] (1) and trans-[PtCl(4)(NCCH(3))(2)] (2))-was investigated extensively by theoretical methods at different levels of theory. The effectiveness of two types of dipolarophile activation (by introducing a strong electron-acceptor group R and by coordination to a metal center) was analyzed and compared. The influence of factors such as the nature of the cyclic nitrone and the nature of the solvent on the reactions was also studied. The reactivity of dipoles and dipolarophiles increases along the series N4 < N1 approximately N3 < N2 and CH(3)CN < CF(3)CN < 1 < 2; the latter demonstrates that the coordination of RCN to a Pt center provides an even higher activation effect upon cycloaddition in comparison with the introduction of a strong electron-acceptor group R such as CF(3). A higher reactivity of the cyclic dipole N1 in comparison with acyclic nitrones (e.g., CH(3)CH=N(CH(3))O) is interpreted to be a result of its exclusive existence in a more strained and hence more reactive E- rather than Z-configuration. The activation and reaction energies have been calculated at different basis sets and levels of theory, up to MP4(SDTQ), CCSD(T), and CBS-Q. The activation energies are weakly sensitive to a change of the correlated methods. The consideration of the solvent effects results in the increase of the activation barriers, and such enhancement is less pronounced for the nonpolar or low polar solvents. The cycloadditions to CH(3)CN and CF(3)CN were found to be nearly synchronous, but these reactions involving 1 and 2 are clearly asynchronous. Moreover, the reaction of N2 with 2 proceeds via a very early acyclic transition state, while for all other reactions the transition states have a cyclic nature.

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Section: Resultsmentioning

confidence: 99%

Theoretical Study of Reactant Activation in 1,3-Dipolar Cycloadditions of Cyclic Nitrones to Free and Pt-Bound Nitriles

Kuznetsov

Kukushkin

2005

J. Org. Chem.

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“…In another report, it was found that steric congestion could not change the reaction mechanism from concerted to stepwise, at least in the 1,3‐dipolar cycloaddition between a nitride ylide and an olefin in an ambient condition . According to present results, factors, such as the nature of 1,3‐dipole dipolarophile , placement of the radical stabilizing functional group on the reactants , existence of electron donor or withdrawing groups on the dipole or dipolarophile , presence of a simple solvent effect having the cluster of solvent molecules with probable intermediate , and the presence of ionic liquids , may be considered as important alternatives with the capability of changing the mechanism of an ordinary 1,3‐DC reactions from concerted into stepwise, or vice versa .…”

Section: Introductionmentioning

confidence: 87%

The Effect of Position Replacement of Functional Groups on the Stepwise character of 1,3‐Dipolar Reaction of a Nitrile Oxide and an Alkene

Siadati

2016

Helvetica Chimica Acta

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It is a well-known fact that by changing the 1,3-dipolar cycloaddition (1,3-DC) reaction mechanism from concerted to stepwise, the stereospecificity is lost; since in synthesizing the required heterocyclic molecules that reaction is a requisite, it is important to study the concertedness of that reaction. Several papers on this subject have already stated that the existence of electron withdrawing groups (EWG) or electron donor groups (EDG) on dipole or dipolarophile leads to a high-energy differentiation between the dipole HOMO and dipolarophile LUMO (or vice versa) as well as the emergence of an intermediate in the reaction pathway. This paper seeks answering the question of when an EWG on dipole and an EDG on dipolarophile could be a factor in making the reaction mechanism stepwise, and does repositioning of functional groups in replacing dipole and dipolarophile switches the reaction mechanism from stepwise into concerted or vice versa?

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Regio‐ and stereoselectivity of [2 + 3] cycloaddition of (E)‐β‐nitrostyrenes to (Z)‐C,N‐diphenylnitrone in the light of AM1 and AM1/COSMO calculations

Cited by 2 publications

References 0 publications

Theoretical Study of Reactant Activation in 1,3-Dipolar Cycloadditions of Cyclic Nitrones to Free and Pt-Bound Nitriles

Theoretical Study of Reactant Activation in 1,3-Dipolar Cycloadditions of Cyclic Nitrones to Free and Pt-Bound Nitriles

The Effect of Position Replacement of Functional Groups on the Stepwise character of 1,3‐Dipolar Reaction of a Nitrile Oxide and an Alkene

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