Magnesium, organo- compounds esters

To prepare our desired product (an ester), we must first synthesize the alcoholic portion of the ester (3-pentanol) from the starting material (ethanol). This can be done by a Grignard reaction. Grignard reagents (organo-magnesium compounds of the type R-Mg-X) will react with carbonyl compounds to produce alcohols upon hydrolysis. 

Like their aryl and alkenyl counterparts, alkynylboronic adds can be made by displacement of magnesium or lithium acetylides with borate esters. For example, Mat-teson and Peacock have described the preparation of dibutyl acetyleneboronate from ethynylmagnesium bromide and trimethyl borate [294]. The C-B hnkage is stable in neutral or acidic hydrolytic solvents but readily hydrolyzes in basic media such as aqueous sodium bicarbonate. Brown and co-workers eventually applied their organo-lithium route to boronic esters to the particular case of alkynylboronic esters, and in this way provided a fairly general access to this class of compounds [295]. 

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