Direct Reduction of Allylic Alcohols Using Isopropanol as Reductant

Abstract

The lithium cation-catalyzed direct reduction of allylic alcohols to alkenes using isopropanol as a hydride donor was developed. The hydride transfer of the in situ-generated lithium isopropoxide to an allylic cation is the key process in this transformation. The reaction generates only water and acetone as byproducts, which highlights the synthetic utility of this method.

An Efficient Ga(OTf)3/Isopropanol Catalytic System for Direct Reduction of Benzylic Alcohols

“…Our investigation began with the screening of Lewis acid catalysts for the direct reduction of benzhydrol 1 a with isopropanol (Table ) . Interestingly, LiPF 6 , which was the optimal catalyst in our previous study, does not catalyze the reaction, resulting in the formation of benzylic isopropyl ether 3 (entry 1) . To realize the desired reduction, it is necessary to cleave the C−O bond of ether 3 effectively.…”

“…Although isopropanol is well‐known as a hydride donor in various reactions, such as Meerwein−Ponndorf−Verley (MPV) reduction and the transfer hydrogenation of carbonyl compounds, there are no reports of the use of isopropanol in the direct reduction of alcohols. In our previous study, we demonstrated for the first time that LiPF 6 can effectively reduce allylic alcohols to alkenes using isopropanol as a reductant . However, this catalytic system is only applicable to highly specialized allylic alcohols, greatly limiting its utility.…”

Direct Synthesis of Indanes via Iron‐Catalyzed Dehydrative Coupling/Friedel–Crafts Cyclization of Two Different Alcohols

“…Initially, we aimed to identify the appropriate catalyst and reaction conditions for the synthesis of indane 2a by the reaction of benzhydrol 1a with tert ‐butyl alcohol (Tableà) and started by testing a Ga(OTf) 3 /PhCF 3 system, which was shown to be highly effective for the C–O bond cleavage in our previous study. [8b] Although this system showed high catalytic activity for the initial dehydrative coupling to afford olefins 3 and 4 ,, the desired indane 2a was obtained in only 10 % yield (entry 1). Next, representative Lewis acids were examined.…”

“…Recently, we have reported new synthetic transformations of unsaturated alcohols involving alcohol C–O bond cleavage by Lewis acids . Based on the results of these studies, we attempted to directly assemble the indane skeleton from two different alcohols, since alcohols are more stable, less volatile, and more readily available than olefins.…”

Bu4NHSO4‐Catalyzed Direct N‐Allylation of Pyrazole and its Derivatives with Allylic Alcohols in Water: A Metal‐Free, Recyclable and Sustainable System

“…General : All the reagents and catalysts were purchased and used without further purification. All allylic alcohols were synthesized according to the literature [19,30] . Analytical thin‐layer chromatography (TLC) plates were purchased from Qingdao Hailang.…”