Sulfides can be readily prepared under mild conditions by a reaction of tetramethylthiourea with alkyl halides and alcohols in the presence of sodium hydride in satisfactory yields. The scope and limitation of this method are also presented.
The first generation of a new sulfur-functionalized nitrile oxide 1,3-dipole, (phenylthio)acetonitrile oxide, is presented. Its cycloadditions to a variety of olefins and acetylenes lead to 3-(phenylthiomethyl)-2-isoxazolines and -oxazoles, the formers being selectively deprotonated at the carbon substituted by the sulfur moiety. The resulting sulfur-stabilized carbanions react with aldehydes, esteric Michael acceptors, and alkyl halides to enable the introduction of a carbon substituent to the side chain on 3-position. Raney Ni reduction of these 2-isoxazolines gives β,β′-dihydroxy ketones and β-hydroxy ketones.
The reaction of the thiourea (I) with the halides (II), followed by reaction of the resulting thiouronium salts with the alcohols (III) in the presence of NaH leads to the sulfides (IV) in fair to good yields.
The isoxazolines (III) are prepared either from the oxime (I) or from the nitro compound (IV); in both cases the reaction involves cycloaddition between the alkenes (II) and the intermediately formed nitrile oxide 1,3‐dipole (V).
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