How to convert a methyl group (-CH3) to a formyl group (-CHO)?

Question

What mechanism(s) is needed to change a methyl group (-CH3) to a formyl group (-CHO)?

Answer 1

One route is to start with a methyl that would then undergo radical chlorination (Chorination is less regioselective towards radicals than bromination) to form alkyl chloride. The alkyl chloride would be reduced to an alkene by treatment with NaOEt followed by an addition reaction to form a primary alcohol (treatment with dilute H2SO4). Finally treating the primary alcohol with PCC and CH2Cl2 would form a formyl group.

 

To summarize the order of the reactions are

 

1) CL2, light

2) NaOEt

3) dilute H2SO4

5) PCC, CH2Cl2

 

Another route is to form the alkene and then perform ozonolysis with O3 and DMS that cleaves the pi bond and form the formyl group.