Which compounds are not useful for preparation of grignard reagents?
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Seems to me that there are solid reasons why NONE of the materials will form Grignards unless they are modified.
1 - The alkyne proton (pKa ~25) will quench any Grignard formed to give the Mg salt
2 - The free base is already unstable in solution wrt aziridine formation/polymerisation; any added base promotes this. Any Grignard formed will also be quenched by the NH2 protons.
3- The -OH proton will quench any Grignard forming the alkoxide which is liable to form the epoxide.
4- Similarly the -OH proton will quench any Grignard forming the alkoxide which can then form the tetrahydrofuran