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Abstract Potential energy surface (PES) analyses at the SMD[MP2/6–311++G(d,p)] level and higher‐level energies up to MP4(fc,SDTQ) are reported for the fluorinated tertiary carbamateN‐ethyl‐N‐(2,2,2‐trifluoroethyl) methyl carbamate (VII) and its parent systemN,N‐dimethyl methyl carbamate (VI). Emphasis is placed on the analysis of the rotational barrier about the CN carbamate bond and its interplay with the hybridization of theN‐lone pair (NLP). All rotational transition state (TS) structures were found by computation of 1D relaxed rotational profiles but only 2D PES scans revealed the rotation‐inversion paths in a compelling fashion. We found four unique chiral minima ofVII, one pair each ofE‐andZ‐rotamers, and we determined theeightunique rotational TS structures associated with every possibleE/Z‐isomerization path. It is a significant finding that all TS structures featureN‐pyramidalization whereas the minima essentially contain sp2‐hybridized nitrogen. We will show that the TS stabilities are affected by the synergetic interplay between NLP/CO2repulsion minimization, NLP→σ*(CO) negative hyperconjugation, and two modes of intramolecular through‐space electrostatic stabilization. We demonstrate how Boltzmann statistics must be applied to determine the predicted experimental rotational barrier based on the energetics of all eight rotamerization pathways. The computed barrier forVIIis in complete agreement with the experimentally measured barrier of the very similar fluorinated carbamateN‐Boc‐N‐(2,2,2‐trifluoroethyl)‐4‐aminobutan‐1‐olII. NMR properties ofVIIwere calculated with a variety of density functional/basis set combinations and Boltzmann averaging over theE‐andZ‐rotamers at our best theoretical level results in good agreement with experimental chemical shifts δ(13C) andJ(13C,19F) coupling constants ofII(within 6 %).
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This content will become publicly available on March 17, 2026
Synthesis of Vinyl Sulfones from Substituted Alkenes via Molybdooxaziridine Catalysis
Abstract Herein we report the MoO2Dipic promoted sulfonation of alkenes using N−Ts‐hydroxylamine as the quantitative source of Ts. The reaction works with high yields and stereoselectivities for styrenes with a wide variety of substitution patterns. A novel atom transfer radical addition mechanism involving the formation of molybdooxaziridine complex1as the active catalyst, difunctionalization withTs‐NO, followed by oxidation, and then elimination as the rate‐determining‐step for the formation of vinylsulfone3has been proposed. Initial kinetic and mechanistic data indicates the formation ofTs‐NOand provides evidence for the proposed mechanism.
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- Award ID(s):
- 1752085
- PAR ID:
- 10609926
- Publisher / Repository:
- European Chemical Societies Publishing
- Date Published:
- Journal Name:
- European Journal of Organic Chemistry
- Volume:
- 28
- Issue:
- 11
- ISSN:
- 1434-193X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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