Treatment of the dichloride A under the conditions indicated gives B with retention of configuration, while treatment of dichloride C gives D with inversion of configuration.

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I am having difficulty drawing out the inversion ring product to find out if the s lone pair can attack from anti to the $\ce{C-Cl}$ σ* bond on the vertical ring. If it does, then, there is retention of product in the first reaction after the $\ce{N3-}$ attacks.

Can someone please help using diagrams?

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    $\begingroup$ See also Converso, A.; Burow, K.; Marzinzik, A.; Sharpless, K. B.; Finn, M. G. 2,6-Dichloro-9-thiabicyclo[3.3.1]nonane:  A Privileged, Bivalent Scaffold for the Display of Nucleophilic Components. J. Org. Chem. 2001, 66 (12), 4386–4392. (dx.doi.org/10.1021/jo015632y) and Díaz, D. D.; Converso, A.; Sharpless, K. B.; Finn, M. G. 2,6-Dichloro-9-thiabicyclo[3.3.1]nonane: Multigram Display of Azide and Cyanide Components on a Versatile Scaffold. Molecules 2006, 11, 212–218. (dx.doi.org/10.3390/11040212); pdf $\endgroup$ – Loong Dec 27 '15 at 15:41
  • $\begingroup$ Is there a typo in compound C? Should those oxygens be there? $\endgroup$ – jerepierre Dec 27 '15 at 15:49
  • $\begingroup$ @jerepierre i thought that too... But i dont think its a typo. $\endgroup$ – justbehappy Dec 27 '15 at 15:54
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    $\begingroup$ C looks OK, but shouldn't the oxygens also be on D? $\endgroup$ – ron Dec 27 '15 at 18:26
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    $\begingroup$ A reacts at low T due to NGP. The sulfur lone pair displaces the Cl, that's the first SN2 and you have inversion of configuration at carbon. Then the azide displaces the sulfur, a second SN2 again with inversion. The net result of 2 inversions is retention of configuration at the carbon initially bound to Cl. In C there are no lone pairs on sulfur, no NGP, higher activation energy, higher temperature needed to get the azide to react via an SN2 with inversion of configuration. $\endgroup$ – ron Dec 27 '15 at 23:00

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