Vinylic functions, hydrogenolysis

Extensive hydrogenolysis of vinyl ethers does not occur always over platinum. Reduction of 28 proceeded smoothly to 29 (/09). It is likely that the high pressure and low temperature used in this experiment helped to minimize hydrogenolysis. For effective use of subambient ( —30°C) temperatures in stopping hydrogenolysis of vinyl functions, see (/Oa). 

Hydrogenolysis of vinylic fluorides is hardly ever done with the aim of removing fluorine finom a molecule. Rather, it occurs as a usually undesirable side reaction, accompanying reductions of other functions in fluorinated compounds. " It frequently takes place during catalytic hydrogenation of fluorinated alkenes. A clear-cut saturation of the double bonds in polyfluorinated alkenes is rare and usually requires mild reaction conditions,and hydrogenolysis of fluorine without reduction of the double bond in catalytic hydrogenation is unknown. Numerous examples are quoted in the review literature, " and a few samples are shown in Table 1. 

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). ... 

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