By Elimination of Functionality from Existing Substituents

Substituents bearing a functional group may be converted into simple alkyl substituents in a variety of ways, illustrated in the following examples  

5-Diethoxy-3-(l-hydroxy-l-methylethyl)pyrazine (155) gave 2,5-diethoxy-3-isopropenylpyrazine (156) (TsOH, PhH, molecular sieves, reflux 80%) 6 2-(l-hydroxy-2-methylpropyl)-6-iodo-3-methoxypyrazine gave 2-iodo-5-methoxy-6-(2-methylprop-l-enyl)pyrazine (157) (TsOH, PhMe, reflux with H20 removal, 6 h 65%).1588 

2-(2-Hydroxyheptyl)-3-methylpyrazine gave 2-(hept-l-enyl)-3-methylpyrazine (TsCl, pyridine, 10°C — reflux, 12 h 45%) also homologues and isomers likewise.352 

Also examples of extranuclear dehydroxylation by other dehydrative methods194, 1239,1377 or reduction384 have been reported. 

Note Hydrogenolysis and other reductive methods appear to be almost unrepresented in recent literature (however, see Section 4.4). 

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