Regiodivergent sulfonylation of terminal olefins <i>via</i> dearomative rearrangement

Blé-González, Ever A.; Isbel, Stephen R.; Ojo, Olatunji S.; Hillesheim, Patrick C.; Zeller, Matthias; Bugarin, Alejandro

doi:10.1039/d3nj03595f

Cited by 1 publication

(1 citation statement)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, we reported the synthesis of α-alkyl styrene using transition metal-free one-pot reaction conducted under mild conditions. − Interestingly, this reaction resulted in a mixture of two distinct styrene derivatives, a and b (Scheme ). Based on the experimental observations in our previously reported work and the bromine-mediated rearrangement reaction studies done by Dubois and Costa, it was proposed that allylaryl undergoes an alkene bromination to form bromonium intermediate I , which later on undergoes an intramolecular rearrangement, a 1,2-shift by the electron-rich aryl moiety to form the spiro[2.5] intermediate II . , The spiro[2.5] intermediate II can be ring-opened by a nucleophilic attack by a Br – anion on the three-membered ring to produce either a 2,3-dibromo derivative ( a ) or a 1,3-dibromo derivative ( b ).…”

Section: Introductionmentioning

confidence: 99%

Quantum Chemical Insight into 1,2-Shift Rearrangement in Bromination of Allylaryls

Hardy,

Isbel,

Bugarin

et al. 2023

ACS Omega

Self Cite

View full text Add to dashboard Cite

In this work, we have provided mechanistic insight into the addition of bromine to an allylic double bond of allylaryl derivatives using experimental and DFT-based electronic structure methods. The experimental yields indicate the influence of the functional group on the aryl ring on the ratio of 1,2-dibromo and 1,3-dibromo adducts formed in the reaction. The optimized geometry and the electron density maps of the allylaryls and their cationic intermediates from DFT simulations revealed that electron-rich aryl rings promoted formation of cationic spiro[2.5] intermediate II, whereas electron-poor aryl rings resulted in formation of bromonium intermediate I. It was observed that electron-rich allylaryls promoted the 1,2-shift of the aryl ring that resulted in bond formation between the carbon atom (C1) on the aryl ring and the central carbon atom (C3) in the allylic double bond and formed spiro[2.5] intermediate II, a trend which was confirmed by harmonic oscillator model of aromaticity index. Also, Wiberg bond order analysis is in good agreement with the experimental work. Thermochemical analysis indicates that smaller C1···C3 distance resulted in favorable values for the difference in free energy change (ΔΔG). The favorable ΔΔG values are a result of higher electron density on the aryl ring, making it more nucleophilic toward C3 carbon and promoting 1,2-shift that led to formation of the spiro[2.5] intermediate. Thus, the underlying mechanism indicates that the electron-rich allylaryls promote the formation of 1,3-dibromo compounds through formation and stabilization of the spiro[2.5] intermediate II.

show abstract