New reactions of carbonyl compounds with organoboranes and haloboranes

The 1,2-addition of organoboranes to carbonyl compounds was investigated utilizing three different approaches. First, the reactions were irradiated with either ultrasound or microwaves, giving, in both cases, negative results. Second, efforts were directed to modify the transition state. Acyloxyboranes gave positive results but improvements will be necessary before the reaction is synthetically useful. Finally, fluorinated organoboranes were prepared in an effort to increase the Lewis acidity at the boron atom. Although no 1,2-addition was observed upon addition to carbonyl compounds, the study led to an unprecedented reaction. It was discovered that ketones react with aromatic aldehydes in non-nucleophilic solvents in the presence of boron trifluoride (and other anhydrous strong acids) to produce β-alkylstyrenes and the corresponding carboxylic acids.