CH3CHO + H2 /Pt → CH3CH2OH
CH3CH2OH + PBr3 → CH3CH2Br
CH3CH2Br + Mg/THF → CH3CH2MgBr
CH3CH2MgBr + 环氧乙烷 → 水解→ CH3CH2CH2CH2OH
CH3CH2CH2CH2OH + CrO3/吡啶溶剂 → CH3CH2CH2CHO （T.M）
总的思路是用格氏试剂和环氧乙烷水解,得到多2个碳原子的醇
然后再氧化得到目标产物