Proton and carbon-13 nuclear magnetic resonance studies of the conformational dynamic properties of seven-membered rings. 2,4-Benzodioxepin and its derivatives

1978 ◽  
Vol 100 (13) ◽  
pp. 4055-4062 ◽  
Author(s):  
A. Blanchette ◽  
F. Sauriol-Lord ◽  
M. St.-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Dynamic Properties ◽  
Magnetic Resonance Studies ◽  
Conformational Dynamic ◽  
Nuclear Magnetic

High-field proton and carbon-13 nuclear magnetic resonance studies of the conformational dynamic properties of seven-membered rings. 1,5-Benzodithiepin and 3-substituted derivatives

1986 ◽  
Vol 64 (11) ◽  
pp. 2142-2151 ◽  
Author(s):  
D. Ménard ◽  
M. St-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperatures ◽  
High Field ◽  
Dynamic Properties ◽  
Magnetic Resonance Studies ◽  
Conformational Dynamic ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The conformational and dynamic properties of 1,5-benzodithiepin (1), its 3,3-dimethyl (2), 3-methyl (3), and 3-methoxy (4) derivatives have been investigated by high-field 1H and 13C dynamic nuclear magnetic resonance methods. Analyses of the spectra at low temperatures indicate that, in CS2, both 1 and 2 exist as a mixture of C and TB forms (97:3 for 1; 63:37 for 2). In contrast, both 3 and 4 exist as a mixture of three equilibrating conformations Ce, Ca, and TB in ratios of 55:25:20 and 88:8:4 respectively. Comparison with analogues derived from 1,5-benzodioxepins (1a–4a) indicates that the replacement of O by S decreases the amount of the TB form for all four compounds studied. The observation that Ce is the most abundant form for 4 while it is not observed for 4a can be explained by a repulsive S/O gauche interaction in 4 compared to an attractive O/O interaction in 4a.

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