Clean Reduction of $\alpha,\beta$-Unsaturated Carboxylic Acid Derviatives to the Saturated Derivatives by Potassium Triphenylborohydride in the Presence of Phenol

${\alpha},{\beta}$-unsaturated carboxylic acid derivatives such as esters, amides, and nitriles are readily reduced to the corresponding saturated derivatives by potassium triphenylborohydride, $KPh_3BH$, in the presence of phenol, a quenching agent, in excellent yields.