Synthesize but from alcohols of 2 carbons or less?

How would you synthesize but, CH3CH2CH2CHO from alcohols of 2 carbons or less, using any needed inorganic reagents? We're doing multistep synthesis in cl. I keep coming up with a need for an alcohol that has more than 2 carbons to make an alkyl halide that makes a Grignard reagent. Thanks for any help you can give.