Molecular modelling studies on the reactions of fluoroalkenes with sulfur trioxide

Morley, John; Roberts, David W.; Watson, Simon P.

doi:10.1039/a902645b

Cited by 8 publications

(1 citation statement)

References 22 publications

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“…−31.4 kcal/mol based on a heat of hydrocarbation of SO 3 of −126 kcal/mol and Δ H f ° (SO 3 , gas) = −94 6 kcal/mol. SO 3 adds to alkenes with high suprafaciality at −60 °C giving the corresponding β-sulfones , that can be rearranged into the corresponding β,γ-unsaturated sulfonic acids . Related to the ene-reaction of SO 2 is the allylic C−H oxidation with SeO 2 − which occur through an initial ene reaction followed by a [2,3]-sigmatropic shift. − The ene-reaction follows a concerted process similar to that proposed for 3 → 2 → 1 .…”

Section: Introductionmentioning

confidence: 99%

Desulfinylation of Prop-2-enesulfinic Acid: Experimental Results and Mechanistic Theoretical Analysis

et al. 2009

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The potential energy surfaces of the desulfinylation of prop-2-enesulfinic acid (13) in CH(2)Cl(2) solution at -15 degrees C have been explored by quantum calculations and analyzed with kinetic data obtained for the reaction in absence or presence of additives. Monomeric 13 adopts a preferred conformation with gauche S=O/sigma(C(1)-C(2) bond pairs and the O-H bond pointing toward C(3). It equilibrates with the more stable dimer (13)(2) (at -15 degrees C) formed by two O-H...O=S hydrogen bonds and in which the S=O/sigmaC(1)-C(2) are gauche also, but the SOH moieties are antiperiplanar with respect to sigma(C(1)-C(2)). Dimer (13)(2) undergoes desulfinylation into propene + SO(2) + 13 following a one-step, concerted mechanism. The preferred transition state is a six-membered, chairlike transition structure (C...S elongation and S-O...H...C(3) hydrogen transfer occur in concert) in which the S=O/sigma(C(1)-C(2)) bonds are gauche (S=O adopt pseudoaxial positions). There are at least 48 transition states, each one defining a different pathway, all with similar calculated free energies (DeltaG(double dagger) = 25.3-28.6 kcal/mol), which makes the bimolecular (autocatalyzed) retro-ene elimination of SO(2) competing (entropy factor) with a monomolecular process for which the transition state (calculated DeltaG(double dagger) = 24.3 kcal/mol) implies only one molecule of sulfinic acid. This agrees with the experimental rate law of the reaction which is first order in the concentration of dimer (13)(2). SO(2), CF(3)COOH, and BF(3) x Me(2)O do not catalyze the reaction. In the presence of an excess of BF(3) x Me(2)O the desulfinylation is completely inhibited due to the formation of a stable tetramolecular complex of type (CH(2)=CHCH(2)SO(2)H x BF(3))(2) (18), for which quantum calculations show that the S=O/sigma(C(1)-C(2)) bonds are antiperiplanar whereas the S-OH/sigma(C(1)-C(2)) bonds are gauche. Independently of the additive, the retro-ene eliminations of SO(2) are calculated to be concerted and have transition states adopting six-membered cyclic structures in which S=O and sigma(C(1)-C(2)) are gauche, the S=O interacting with the additive. Preliminary experiments suggested that the thermodynamically unfavored ene reaction of SO(2) with propene can occur at low temperature using 1 equiv of BF(3).

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Section: Introductionmentioning

confidence: 99%

Desulfinylation of Prop-2-enesulfinic Acid: Experimental Results and Mechanistic Theoretical Analysis

et al. 2009

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Sulfur Dioxide: A Powerful Tool for the Stereoselective Construction ofCCBonds

Vogel

Marković

Turks

2013

Stereoselective Synthesis of Drugs and Natural Products

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For a long time, the use of sulfur dioxide in organic chemistry was limited to the synthesis of simple bulk materials such as sulfinate salts and sulfones. Conjugate bases of sulfones are carbon nucleophiles that can be used to construct CC single bonds and stereoselective CC double bonds. Sulfones can also be employed as electrophiles, for instance, in the stereo‐ and enantioselective α‐aminoalkylations of carbonyl compounds. α,β‐Unsaturated sulfones are excellent acceptors in asymmetric Michael additions. They are also good dienophiles. Sulfones and readily available sulfonyl chlorides are good electrophilic partners in desulfinylative CC cross‐coupling reactions catalyzed by transition metals, including iron. Sulfur dioxide undergoes reversible cheletropic additions with 1,3‐dienes and irreversible metallo‐ene reactions with allylmetals. Conditions have been found realizing the endergonic H‐ene reactions of SO 2 with alkenes. This permits the one‐pot synthesis of polyfunctional sulfinates, sulfones, and sulfonamides starting from alkenes. At a low temperature, the hetero‐Diels‐Alder additions of SO 2 generate unstable sultines that can be used as electrophiles in the stereoselective construction of CC bonds between electron‐rich alkenes and 1,3‐dienes. The reaction cascade permits the one‐pot construction of stereotriads and stereotetrads that can be used subsequently in two successive aldol reactions that give, in short ways (double chain elongation), long‐chain polyketide and polypropionate antibiotics.

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Regioselectivity in Iron‐Catalyzed [2+2+1] Cycloadditions: A DFT Investigation of Substituent Effects in 1,4‐Diazabutadienes

Imhof

Anders

2004

Chemistry A European J

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The transition-metal-catalyzed [2+2+1] cycloaddition reaction of 1,4-diazabutadienes, in which the imine-carbon atoms are part of an oxazine ring system, with ethylene and carbon monoxide leads to the regioselective formation of pyrrolidinone derivatives. To explain this regioselectivity, the transition states and intermediates of the rate-determining step of the catalysis are determined by high-level DFT calculations. The experimentally observed regioselectivity is consistent with the lower activation energy of the addition of ethylene towards the carbon atom next to the oxazine oxygen atom. Furthermore, the activation barrier of a conceivable back reaction is higher for the intermediates with the experimentally observed regioselectivity. These thermodynamic and kinetic arguments at first sight appear to be confirmed by the calculated NPA charges in the transition states, which reveal that the differences in these charges are greatest for those transition states that lead to the formation of the energetically favored transition structures. Nevertheless, calculations of analogous transition structures and reaction products starting from 1,4-diazabutadienes with a 2-fluoro, 2-hydroxo or 2-amino substituent revealed that the regioselectivity is not determined by the electronegativity of the heteroatom and thus by the differences in the NPA charges or the resulting Coulombic interactions in the transition structures. The main reason for the observed regioselectivities is the pi-donor ability of the substituent to contribute to a delocalized pi system incorporating the adjacent imine moiety. The increasing pi-donor capability results in decreased reactivity of this moiety and increases the (relative) reactivity of the second imine group. This effect can even overcompensate for strong intramolecular Coulombic attractions in the transition structures.

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Molecular modelling studies on the reactions of fluoroalkenes with sulfur trioxide

Cited by 8 publications

References 22 publications

Desulfinylation of Prop-2-enesulfinic Acid: Experimental Results and Mechanistic Theoretical Analysis

Desulfinylation of Prop-2-enesulfinic Acid: Experimental Results and Mechanistic Theoretical Analysis

Sulfur Dioxide: A Powerful Tool for the Stereoselective Construction ofCCBonds

Regioselectivity in Iron‐Catalyzed [2+2+1] Cycloadditions: A DFT Investigation of Substituent Effects in 1,4‐Diazabutadienes

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