[2,3]‐sigmatropic rearrangements of hydrogen and alkyl 3‐propenyl sulfoxides: A computational study

Abstract

The [2,3]-sigmatropic rearrangements of hydrogen and alkyl 3-propenyl sulfoxides (R ϭ H, CH 3 , CF 3 , CCl 3 ) to the corresponding 3-propenyl sulfenates have been examined computationally using HF, MP2, and B3LYP with the 6-31G(d), 6-31ϩG(d,p), 6-311ϩG(d,p), 6-311ϩG(2d,2p), 6-311ϩG(3d,2p), and cc-pVTZ basis sets. The relative energies (E rel ) of the respective isomeric sulfoxides and sulfenates are sensitive to the level of theory and to electron correlation. The sulfenate is more stable in the gas phase, and the more polar sulfoxide is more stable in aqueous medium. The rearrangements are concerted, and the endo and exo five-membered transition states are very close in energy (⌬E ϭ Ͻ1 kcal/mol). MP2/6-311ϩG(3d,2p) predicted the activation barriers for the sulfoxide-sulfenate rearrangements to be [kcal/mol, (R)] 19.0 (H), 21.4

Dynamic Kinetic Resolution of Allylic Sulfoxides by Rh-Catalyzed Hydrogenation: A Combined Theoretical and Experimental Mechanistic Study

“…28 Structures were optimized in the gasphase with M06 29 and a mixed basis set of SDD for rhodium and 6-311+G** for all other atoms. The need for a large basis set to accurately calculate the thermodynamics of the 2,3-rearrangement of allylic sulfoxides has previously been noted in several studies, 15,30–32 and we confirmed this in our own benchmarking studies. Frequency calculations were performed to check the nature of the stationary points and obtain free energies.…”

A theoretical study of the sulfenate–sulfoxide rearrangement. Effect of the hydrogen bond complexation

“…This mechanism was confirmed later in an experimental study of the thermolysis of the cinnamyl-4-nitrobenzenesulfenate [9]. Freeman et al [8] studied the [2,3]-sigmatropic rearrangement in hydrogen and alkyl 3-propenyl sulfoxides. These authors found that the rearrangements are concerted and that the endo and exo five-membered TS's are very close in energy.…”

“…Two articles have explored theoretically the mechanism of this reaction [7,8]. Amaudrut et al [7] found three possible mechanisms in the reaction of the parent compound, two-concerted transition states (TS's) corresponding to a suprasuprafacial pathway, and a supra-antarafacial pathway and a stepway mechanism that proceeds via radicalic intermediates.…”

Molecular Rearrangements: Part 1. Pericyclic Reactions

“…Allyloxyphosphonium ylids (32), generated in situ, have been shown to undergo [3,3]-sigmatropic rearrangements readily on heating to give phosphonate derivatives (33) in good yields. Diastereoselectivity has been found to be low; following DFT cal-de culations, this has been attributed to the small energy gap between axial and equatorial ylid substituents, because of the long P-C ylid bond.…”

“…32 A DFT study of the [2,3]-sigmatropic rearrangements of some hydrogen and alkyl prop-3-enyl sulfoxides to the corresponding prop-3-enyl sulfenates has found the rearrangements to be concerted, with the competing exo and endo transition states very close in energy. 33 Enantiomerically pure branched allylic alkyl sulfides (39) ee have been shown to give N -allylic-N -Boc-sulfimides (40) via a [2,3]-sigmatropic rearrangement, with essentially complete transfer of chirality, on treatment with NBoc-3,3-di(ethoxycarbonyl)oxaziridine. 34…”