Frontier molecular orbitals of 1,3 dipoles and dipolarophiles

Houk, K. N.; Sims, Joyner.; DUKE, R. E. JUN.; Strozier, Robert W.; George, John K.

doi:10.1021/ja00803a017

Cited by 589 publications

(186 citation statements)

References 11 publications

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“…As can be observed, the three atoms belonging to this TAC present negative charges: -0.30e (C1), -0.18e (N2) and -0.54e (N3), while the hydrogen atoms support the positive charges. This charge distribution is in complete disagreement with the commonly accepted 1,2-zwitterionic structure given for AIs in which a positive charge and a negative charge are entirely located at the N2 and N3 nitrogen atoms [3,22].…”

Section: Elf Topological Analysis and Natural Population Analysis (Npcontrasting

confidence: 85%

A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

Domingo

Ríos‐Gutiérrez

2017

Preprint

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Abstract:The electronic structure and the participation of the simplest azomethine imine (AI) in [3+2] cycloaddition (32CA) reactions have been analysed within the Molecular Electron Density Theory (MEDT) using DFT calculations at the MPWB1K/6-311G(d) level. Electron localisation function (ELF) topological analysis reveals that AI has a pseudoradical structure, while the conceptual DFT reactivity indices characterise this TAC as a moderate electrophile and a good nucleophile. The non-polar 32CA reaction of AI with ethylene takes place through a one-step mechanism with low activation energy, 5.3 kcal/mol -1 . A bonding evolution theory (BET) study indicates that this reaction takes place through a non-concerted [2n+2τ] mechanism in which the C−C bond formation is clearly anticipated prior to the C−N one. On the other hand, the polar 32CA reaction of AI with dicyanoethylene takes place through a two-stage one-step mechanism. Now, the more favourable regioisomeric transition state structure (TS) is located 8.5 kcal·mol -1 below the reagents, in complete agreement with the high polar character of the TS. The current MEDT study makes it possible to extend Domingo's classification of 32CA reactions to a new pra-type of reactivity.

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Section: Elf Topological Analysis and Natural Population Analysis (Npcontrasting

confidence: 85%

A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

Domingo

Ríos‐Gutiérrez

2017

Preprint

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“…30 For methyl azide, the proximal nitrogen has a larger coefficient than the distal nitrogen (Figure 3). 31 It is likely that the same regioisomeric preferences would be observed regardless of stepwise nucleophilic attack of azide upon oxyallyl cation or in a HOMO azide -LUMO oxyallyl cation controlled [3+3] concerted reaction.…”

Section: Discussionmentioning

confidence: 99%

Reactions of Cyclopropanone Acetals with Alkyl Azides: Carbonyl Addition versus Ring-Opening Pathways

et al. 2007

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The Lewis acid-mediated reactions of substituted cyclopropanone acetals with alkyl azides were found to strongly depend on the structure of the ketone component. When cyclopropanone acetal was treated with alkyl azides, N-substituted 2-azetidinones and ethyl carbamate products were obtained, arising from azide addition to the carbonyl, followed by ring expansion or rearrangement, respectively. When 2,2-dimethylcyclopropanone acetals were reacted with azides in the presence of BF 3 •OEt 2 , the products obtained were α-amino-α′-diazomethyl ketones, which arose from C2-C3 bond cleavage of the corresponding cyclopropanone, giving oxyallyl cations, that were captured by azides. Aryl-substituted cyclopropanone acetals, when subjected to these conditions, afforded [1,2,3] oxaborazoles exclusively, which were also the result of C2-C3 bond rupture, azide capture and then loss of nitrogen. In the reactions of n-hexyl-substituted cyclopropanone acetals with alkyl azides, a mixture of 2-azetidinones and regioisomeric [1,2,3]oxaborazoles were obtained. The reasons for the different behavior of the various systems is discussed.Cyclopropanones display unusual properties arising from the incorporation of the carbonyl group into a strained three-membered ring. 1 Initially, cyclopropanones attracted interest due to their role as intermediates in Favorskii rearrangements. 2 Since then, there have been numerous experimental and theoretical studies aimed at understanding the nature of cyclopropanone reactivity. 3 Inherently reactive, cyclopropanones are usually generated in situ from the corresponding hemiketals (or their derivatives), which are readily synthesized and easily handled (Scheme 1). 4 In general, the chemistry of cyclopropanones is dominated by ketone addition or ring-opening to form oxyallyl cations. 5 The latter species can be trapped with a nucleophile 6 or cyclized with a dipolarophile to give bicyclic ketones. 7In the 1970's, Wasserman et al. showed that cyclopropanones react with sodium azide, to afford β-lactams (Scheme 2). 8 This reaction presumably proceeds due to the release of strain upon ring expansion coupled with the generation of nitrogen as the byproduct. Our group has previously studied the intermolecular reaction of alkyl azides with cyclic ketones, which generally leads to ring-expanded lactams in a process reminiscent of the Schmidt reaction. 9 Following Wasserman, we were initially interested in reacting cyclopropanones with alkyl azides under Lewis acidic conditions as a means of synthesizing N-substituted β-lactams. In the course of this study, we discovered that the Lewis acid promoted reactions of azides and cyclopropanones provide a rich array of products that depend on the nature of the cyclopropanone substitution. Previously, we disclosed that the reactions of 2,2-dimethylcyclopropanone equivalents with azides provide α-amino-α2-diazomethyl ketones. 10 Herein, we describe the results of a broader investigation on the reactions of substituted cyclopropanones with alkyl azides. In s...

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“…13 This trend in reactivity has been documented in the literature for other bimolecular reactions. [31][32][33][34][35] Houk and Ess examined cycloadditions of hydrazoic acid, an ambiphilic 1,3-dipole, to a series of substituted alkenes and found that electron-rich and electron-deficient alkenes lower the activation barriers ~2 kcal mol -1 compared to ethylene. 30 From the distortion/interaction analyses in Figure 3, medium-range (d ~ 3 Å) attractive interactions exist while there is yet no distortion between the carbene and ethylene.…”

Section: Cycloadditions To Ethylenementioning

confidence: 99%

Distortion/interaction analysis of the reactivities and selectivities of halo– and methoxy–substituted carbenes with alkenes

Sader¹,

Houk²

2014

Arkivoc

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Dedicated to Pierre Vogel, a great scientist and friend, on his 70 th birthday DOI: http://dx.doi.org/10.3998/ark.5550190.p008.408 AbstractThe transition structures for the (2+1) cycloadditions of dichlorocarbene, chlorofluorocarbene, and difluorocarbene to cyclohexene, 1-hexene, ethylene, and α-chloroacrylonitrile were located using quantum mechanical methods (M06-2X). In addition, transition structures for the (2+1) cycloadditions of chloromethoxycarbene, fluoromethoxycarbene, and dimethoxycarbene to ethylene and α-chloroacrylonitrile were computed. Except for the reactions with ethylene, these cycloadditions were studied experimentally and computationally by Moss and Krogh-Jespersen (Zhang, M.; Moss, R. A.; Thompson, J.; Krogh-Jespersen, K. J. Org. Chem. 2012, 77, 843-850). As a complement to the work of those groups, we have utilized the distortion/interaction model to understand reactivities and selectivities. Gas-phase calculations were carried out at the M06-2X/6-31+G(d,p) level of theory.

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Frontier molecular orbitals of 1,3 dipoles and dipolarophiles

Cited by 589 publications

References 11 publications

A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

Reactions of Cyclopropanone Acetals with Alkyl Azides: Carbonyl Addition versus Ring-Opening Pathways

Distortion/interaction analysis of the reactivities and selectivities of halo– and methoxy–substituted carbenes with alkenes

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