Lithium borohydride unsaturated carbonyl compounds

For the more reactive nucleophiles, where addition is essentially irreversible, whether 1,2-addition or 1,4-addition occurs depends on the relative rates of addition to the two electrophilic sites, the carbonyl carbon and the /3-carbon. Lithium aluminum hydride usually gives predominantly 1,2-addition and provides a useful way to reduce the carbonyl group of an a,/3-unsaturated compound. Sodium borohydride, on the other hand, often gives a mixture of 1,2-addition and the completely reduced product, where 1,4-addition followed by 1,2-addition has occurred. Thus, the reaction of 2-cyclohexenone with lithium... 

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