Stereoselective reduction of 4-tert-butylcyclohexanone to cis-4-tert-butylcyclohexanol catalysed by zeolite BEA

Abstract

Zeolite BEA is found to be the first stereoselective and regenerable heterogeneous catalyst for the Meerwein-Ponndorf-Verley reduction of 4-tert-butylcyclohexanone to cis-4-tert-butylcyclohexanol.The Meenvein-Ponndorf-Verley (MPV) reduction of aldehydes and ketones is a highly selective reaction that can be performed under mild conditions, without affecting other reducible functional groups. The hydrogen donors are easily oxidizable secondary alcohols and the reductions are usually catalysed by metal alkoxides such as A1(OPrl)3. The catalytic activity of metal alkoxides is related to their Lewis acidic character in combination with ligand exchangeability. A major advantage of heterogeneous over homogeneous catalysts is that they can easily be separated from the liquid reaction mixture. However, only a few examples of heterogeneously catalysed MPV reductions have been reported.'The stereoselective reduction of 4-tert-butylcyclohexanone to cis-4-tert-butylcyclohexanol is a commercially interesting conversion. The cis-alcohol is in use on a substantial scale as an intermediate in the fragrance industry. However, the homogeneous MPV reduction of 4-tert-butylcyclohexanone cata-

Gas-phase Meerwein–Ponndorf–Verley reaction: correlation of the 3665 cm−1 IR band with the cis-alcohol selectivity

“…This is consistent with the literature data for the MPV reactions in the liquid phase [7,25] as well as the gas-phase results that were obtained using a higher partial pressure of IPA [24]. Higher cis-than tr-4-TBCHL selectivity in the zeolite Beta-catalyzed MPV reactions is hypothesized to be due to the fact that the cis-transition state can be easily accommodated within the straight channels of zeolite Beta, whereas the bulkier tr-transition state cannot [26]. As illustrated in Fig.…”

Recent development of asymmetric syntheses based on the Meerwein‐Ponndorf‐Verley reduction

“…43,44 Several methods of activation of aluminum isopropoxide, e.g., by microwave irradiation, 45 by zeolite, 46 and by grafting on MCM-41, 47 have been recently studied. Inorganic Mg-Al hydrotalcite was also used as a catalyst of the MPV reduction.…”

Zeolites as Catalysts for the Synthesis of Fine Chemicals

“…Al-and Ti-zeolites have been reported as excellent catalysts for MPVO reactions, and it was shown that Lewis acid sites were the active sites of the catalyst. Thus, Creyghton et al [188,189] reported the stereoselective reduction of 4-tert-butylcyclohexanone to cis-4-tert-butylcyclohexanol (>95%) (which is a fragrance chemical intermediate) in liquid phase using Beta zeolite as catalyst (Scheme 25.36).…”