Assignments of configuration by nuclear Overhauser effects in some dibenzthiepin derivatives

Abstract

The configuration of the benzylic protons responsible for each absorption in the nuclear magnetic resonance spectra of 1,ll-dimethyl-5,7-dihydrodibenz(c,e)thiepn and its S-oxide and S-dioxide have been determined by nuclear Overhauser experiments. Successful application of the method was achieved by using partially deuterated derivatives for the purpose of removing undesirable relaxation mechanisms between protons. Triple irradiation of doublets was also usefully employed. The sulfoxide assignnlents arrived at herein reverse the tentative assignments put forth by us (1). It is noteworthy that all experiments on the sulfoxide failed when CDCl, was used as solvent. I n DMSO normal nuclear Overhauser effects were seen, presumably since sulfoxide dimers are not formed in this solvent. The sulfonium perchlorate derivative of the thiepin was also synthesized. The remarkable similarity of its n.m.r. spectrum to that of the sulfoxide is interpreted as evidence that the effect of the sulfoxide group on the shifts of neighboring protons is due primarily to the "lone pair" on sulfur.L'utilisation de I'effet Overhauser nuclkaire a permis de determiner la configuration des protons benzyliques dans la dimethyl-1,ll dihydro-5,7 dibenz(r,e)thiCpine, aussi que dans le sulfoxyde et la sulfone dCrives. Les resultats obtenus pour le sulfoxyde inversent I'attribution de configuration precedemment publike (1). 11 est a noter que I'observation d'effets est liee a certaines conditions; (a) utilisation de composCs partiellement deutCries afin d'eliminer des phinomenes de relaxation indesirables; (b) dans le cas du sulfoxyde les experiences ont Ctt negatives dans CDCl, et positives dans DMSO-4, solvant dans lequel le sulfoxyde n'est vraisemblablement pas sous forme dirnere. La triple irradiation de doublets a aussi etC utilisie avec succes. Le perchlorate du methyl sulfonium de la thiCpine a Cte prepare. Son spectre de resonance magnetique nucleaire presente une grande analogie avec celui du sulfoxyde. Ceci tend a montrer que I'effet du sulfoxyde sur le deplacement chimique des protons adjacents est dfi principalement au doublet libre du soufre.

Solvent effect on the conformational preference of the carbanions derived from benzyl methyl sulfoxide

“…2The tentative stereochemical assignments made in this paper have been shown to be in error and have been corrected (10). they compare favorably with those obtained by nuclear magnetic resonance (n.m.r.)…”

Chromatographic Resolution, Circular Dichroism Spectra, Absolute Configurations, and Crystal Structures of Bridged Biphenyls, Containing Sulfide, Sulfoxide, and Sulfone Groups in the Bridge

“…± Materials. Compounds 1 and 4 have been described by Mislow et al [4], and 2 and 3 by Frazer and Schuber [9]. Our syntheses were performed mainly according to these procedures, but the key intermediate 6,6'-dimethyl-[1,1'-diphenyl]-2,2'-dicarboxylic acid was prepared via the diazonium salt of 3methylanthranilic acid [10].…”

“…(m.p. 137 ± 1388 ( [9]: 137 ± 1388)). In spite of numerous attempts, crystals of better quality could not be obtained.…”

“…The sulfone 3 was obtained as good crystals (m.p. 221 ± 2228 ( [9]: 221 ± 2228)) by recrystallization from acetone. Crystals of 4 (m.p.…”

Organic Sulfur Mechanisms. 15. The Stereochemistry of α-Hydrogen Exchange in the Simple Cyclic Sulfoxide 1,3 Dihydrobenzo[c]thiophene 2-Oxide

“…J. Chem., 51,4082 (1973) Asymmetric induction in reactions involving a-sulfinyl carbanions and related species has been much studied in recent years (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), though a truly predictive theoretical description of these reactions for practical use has not as yet been elaborated. In the hope of contributing to the development of such a rationale we describe our observations with 1,3-dihydrobenzo[c]thiophene 2-oxide (I), a simple cyclic sulfoxide in which the asymmetric induction derives entirely from one prochiral sulfur atom and in which a number of the steric features of these reactions can be seen very easily.…”