Treatment of Grignard reagents with aldehydes

Treatment of aldehydes with Grignard reagents affords secondary alcohols in accord with the following scheme of addition  

For example, Coburn195 describes the preparation of 3-penten-2-ol196 in 85% yield on addition of an ethereal solution of crotonaldehyde dropwise with stirring and cooling to an ethereal solution of methylmagnesium chloride (from magnesium and methyl chloride)  

Correspondingly, primary alcohols are formed from formaldehyde and a Grignard reagent. CH2o + RMgX — RCH2OH 

Newman and Wotiz196 used this reaction to synthesize 2-heptyn-l-ol, the requisite Grignard reagent being obtained from 1-hexyne and ethylmagnesium bromide  

The 2-heptynylmagnesium bromide obtained in this way affords the 2-hep-tyn-l-ol on reaction with formaldehyde  

---