Transmission of Substituent Effects through Oxygen and Sulfur Atoms. I. 1H Chemical Shifts of Ring-substituted Phenyl Vinyl Ethers and Sulfides

Abstract

The proton chemical shifts of the vinyl group in ring-substituted phenyl vinyl ethers (PVE) and sulfides (PVS) were measured and related to the Hammett σ constants. It was found that the ρ value for the β-trans proton of PVS, −0.448 τ⁄σ, is greater in magnitude than that of PVE, −0.378 τ⁄σ, in contrast to the tendency reported for the methyl hydrogens in anisole and thioanisole. The results can best be explained in terms of the concept of the through-conjugative (pπ-dπ-pπ) behavior of the sulfur atom interposed between two unsaturated groups.

Cross-Coupling Reactions of Hypervalent Siloxane Derivatives: An Alternative to Stille and Suzuki Couplings

“…4-Allyltoluene (9): TLC R f = 0.55 (pentane); IR (CCl 4 ) 3126 (w), 3082 (m), 3049 (s), 3005 (s), 2980 (s), 2923 (s), 2853 (m), 1639 (s), 1576 (s), 1514 (s); 1 H NMR (200 MHz, CDCl 3 ) δ 2.31 (s, 3H), 3.34 (d, J = 6.7, 2H), 5.01 (t, J = 1.4, 1H), 5.06−5.10 (m, 1H), 5.88−6.02 (m, 1H), 7.04−7.20 (m, 4H); 13 C NMR (CDCl 3 ) δ 21.0, 39.8, 115.5, 126.8, 128.4, 129.1, 135.5, 137.8; LRMS (EI) 132 ((M + ), 12), 131 (13), 117 (81), 91 (100); HRMS (EI) calcd for C 10 H 12 132.0939 (M + ), found 132.0940. The 1 H NMR matched spectral data found in ref .…”

Synthesis and Electronic Factors in Thermal Cyclodimerization of Functionalized Aromatic Trifluorovinyl Ethers

“…This trend is observed in both the cis and trans (to O) fluorine signals; however the geminal fluorine signals move upfield with increasing electron-withdrawing character as previously recognized for other fluorovinyl ethers (Table ) . This effect on the geminal fluorine contradicts what is observed in 1 H NMR for nonfluorinated substituted phenyl vinyl ethers . A plot of the average 19 F NMR shift versus the Hammett substitution constant σ p 14 shows a linear relationship (Figure ).…”

“…NMR chemical shifts can be a useful indication of substitution effects at a particular location and has been used frequently as a means of estimating Hammet substituent constants. For example, the effects of substitution were shown to transmit better through nonfluorinated vinyl ethers than for analogous allyl or styryl systems . In addition to NMR shifts, the p K a of a substituted phenoxyacrylic acid was measured and the Hammett relationship determined .…”