Lithium aluminum hydride reduction of 1-phenylbutane-1,3-dione, and acetylation of the products: NMR and GC-MS analysis

Abstract

Reduction of ?-diketones with lithium aluminum hydride (LiAlH4, LAH) can lead to different products, depending on the tautomeric equilibrium: the reduction of diketo forms gives the corresponding diols and the reduction of ketoenol forms yields elimination products, saturated and unsaturated ketones and alcohols. Here, we report on the results of LAH reduction of 1-phenylbutane-1,3-dione. The products of reduction were further acetylated and separated by dry flash chromatography. The obtained products, phenylbut(en)ols, phenylbut(en)ones and phenylbut(en)yl acetates, were characterized by spectral (1H and 13C NMR, MS) and retention index (RI) data. It can be concluded that LAH preferentially reduces the carbonyl group more distant from the phenyl group of 1-phenylbutane-1,3-dione. The structure-retention index relationships between isomers were discussed. Proton splitting patterns were resolved by proton NMR simulations.