Sulfoxides sulfoxide/lithium displacement

Sulfur-lithium exchange is easier and has much greater potential (much of it still unrealised) when the sulfur is at the sulfoxide oxidation level. It has long been known that organolithiums, like Grignard reagents, will attack a sulfoxide, displacing with inversion at sulfur the substituent best able to support an anion. The reaction has been commonly used to form sulfoxides with defined stereochemistry 152157... 

Displacements Boron trifluoride etherate. N,N-Diethyl-l,2,2-trichlorovinylamine. Dimethyl sulfoxide. Hexamethylphosphoric triamide. Lead acetate. Lithium bromide. Magnesium bromide. Polyphosphoric acid. Tetraethylammonium acetate. 

The use of acetic anhydride as the solvent facilitates432 intermolecu-lar iodide displacements at C-5 of 156. Acylation of the heterocyclic base occurred at N-l (as indicated by infrared spectroscopy) during the reaction, and this inhibited occurrence of intramolecular displacement. The electron-withdrawing effect of the acyl group presumably diminishes the nucleophilicity at N-3. N-Formyl-2, 3 -0-iso-propylidene-5 -0-p-tolylsulfonyladenosine also reacts intermolecu-larly with lithium chloride or sodium azide in methyl sulfoxide to give 5 -chloro and 5 -azido derivatives.432... 

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