Conformational analysis XX—¹³C NMR studies of saturated heterocycles 5—substituent effects on the ¹³C chemical shifts of methyl substituted 1,3‐dithiolanes

Abstract

The 13CNMR chemical shifts for 1,3-dithiolane and 13 methyl substituted derivatives are reported. Substituent effects are derived and compared with those for cyclopentanes and 1,3-dioxolanes. The magnitude and variety of the substituent effects are best explained with the aid of a half-chair conformation where the S-1-C-2-S-3 plane passes between C-4 and C-5.

Substituent effects on 13C chemical shifts of alkyl‐substituted 4‐oxo‐1,3‐dioxolanes and 5‐oxo‐1,3‐oxathiolanes

“…In solving these equations, no orientational differentiation was made for the substituents except for the cis-or trans-disubstitution as was the case for 1,3-dithiolanes. [16] The additional SE(2,5,5-triMe) effect, however, shows that also in 1 the methyl groups do have some equatorial and axial character. The 2,5-(5 + 6) [2,4 -6] and 2,4-disubstituted derivatives (15 + 16 and 19+20) [16] cannot be separated.…”

“…[16] The additional SE(2,5,5-triMe) effect, however, shows that also in 1 the methyl groups do have some equatorial and axial character. The 2,5-(5 + 6) [2,4 -6] and 2,4-disubstituted derivatives (15 + 16 and 19+20) [16] cannot be separated. Hence 13 C NMR spectroscopy offers an effective tool for their structural study.…”

Identification and Characterization of Sulfur Heterocyclic Compounds That Contribute to the Acidic Odor of Aged Garlic Extract

“…The position of the cis−trans isomer was determined by comparing the NMR data to that in previous report. 26 Compound 1 exhibits two asymmetric centers, and thus, has four stereoisomers. All four isomers were synthesized to determine the absolute configuration of 1 (Figure 2).…”

“…The identities were subsequently confirmed by matching their mass spectra, RIs, 1 H NMR spectra, and odor qualities with those of the synthesized authentic compounds. The position of the cis – trans isomer was determined by comparing the NMR data to that in previous report …”

“…Compound 2 was synthesized according to the method of Iranpoor and Owji. 22 1 H NMR for (2S,5S)-2 and (2R,5R)-2 (400 MHz, CDCl 3 ): δ 1.41 (d, 6H, J = 6.8 Hz), 2.74−2.82 (m, 2H), 2.94−3.03 (m, 4H); MS-EI m/z (intensity in relative %): 41 (19), 45 (33), 59 (24), 60 (88), 74 (26), 75 (50), 88 (8), 106 (42), 133 (5), 148 (100; M + ). 1 H NMR for meso-trans-2 (400 MHz, CDCl 3 ): δ 1.21 (d, 6H, J = 6.8 Hz), 2.54− 2.70 (m, 4H), 3.12−3.22 (m, 2H); MS-EI m/z (intensity in relative %): 41 (17), 45 (18), 59 (20), 60 (68), 74 (22), 75 (35), 106 (38), 133 (6), 148 (100; M + ).…”