Vinyl iodides hydrogenolysis

Upon deprotection of the benzyl group under hydrogenolysis conditions, and oxidation of the resulting primary alcohol to the corresponding aldehyde with Dess-Martin periodinane [74], compound 137 was obtained. Aldehyde 137 is the coupling partner for the NHK reaction with the vinyl iodide 82. 

This method offers high functional group tolerance as electron-withdrawing groups and free hydro)g ls are tolerated. In addition to aryl and vinyl iodides, aiyl bromides may also be used but typically provide lower yields. A variant employing aryl boronic acids in place of aryl halides was also reported. Additionally, primary sulfonamides are accessible by a hydrogenolysis/Zn reduction sequence (Scheme 13.18). ... 

In the reaction of Q,/3-unsaturated ketones and esters, sometimes simple Michael-type addition (insertion and hydrogenolysis, or hydroarylation, and hydroalkenylation) of alkenes is observed[53,54]. For example, a simple addition product 56 to methyl vinyl ketone was obtained by the reaction of the heteroaromatic iodide 55[S5]. The corresponding bromide affords the usual insertion-elimination product. Saturated ketones are obtained cleanly by hydroarylation of o,/3l-unsaturated ketones with aryl halides in the presence of sodium formate, which hydrogenolyses the R—Pd—I intermediate to R— Pd—H[56]. Intramolecular hydroarylation is a useful reaction. The diiodide 57 reacts smoothly with sodium formate to give a model compound for the afla-toxin 58. (see Section 1.1.6)[57]. Use of triethylammonium formate and BU4NCI gives better results. 

Vinyl isonitriles 693 can be deprotonated with LDA in THF at —78 °C to give the vinyl-lithium 694, which has been used as a 3-hydroxypropanoyl anion equivalent. Intermediate 694 reacted with primary alkyl iodides and bromides to form alkylated products 695 and, after hydrolysis, the corresponding ketones, which can be submitted to hydrogenolysis, leading to -hydroxyethyl ketones in good yields (66-90%)"8 (Scheme 180). 

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