Abstract
The 1-propenyl ethers bearing free hydroxyl groups of CH3CH=CH–O–A–OH type (hydroxyalkyl 1-propenyl ethers, 1-propenyloxyalcohols) are the most desired as the reactive diluents for photopolymerizable systems with enhanced reactivity or intermediates for the synthesis of hybrid monomers for special applications. The ruthenium complexes-catalyzed isomerization of allyl ethers under solvent-free conditions is an atom-economical and environmentally sustainable method for their production. Here, the reaction conditions and limitations for the highly productive and selective synthesis of model 4-(1-propenyloxy)butan-1-ol have been investigated. The minimal loading of ruthenium pre-catalysts needed for completion of reaction within reasonable times was priority assumption. It was found that [RuClH(CO)(PPh3)3] or [RuCl2(PPh3)3] exhibited extremely high catalytic activity under optimized non-oxidative reaction conditions. The key effect of reaction temperature on the activation pre-catalyst and the exothermal effects of isomerization was discovered. The practically quantitative yields of 4-(1-propenyloxy)butan-1-ol were achieved with using of very low loading of [Ru] (5 ppm) and Bu3N (to maintain reaction chemoselectivity) at the temperature of 120 °C for only 0.5 h. Consequently, the attained TON (turnover number) and TOF (turnover frequency) values of ca. 198,000 and 390,000 h−1 were unprecedentedly high and industrial attractive. On the other hand, the direct recycling of ruthenium catalyst is not a reasonable method for improving catalyst productivity.
Highlights
During the last 30 years, the use of homogeneous catalysis with soluble transition metal complexes (TMCs) for the fine chemical, chemical specialties, pharmaceutical and polymer production is rapidly expanding
The isomerization of alkenes and their derivatives catalysed by TMCs is well-recognised in academic and industrial organic chemistry [6,7,8]
We demonstrated that the difficulty in the conducting of the allyloxyalcohols isomerization in
Summary
During the last 30 years, the use of homogeneous catalysis with soluble transition metal complexes (TMCs) for the fine chemical, chemical specialties, pharmaceutical and polymer production is rapidly expanding. Among TMCs, those from platinum group metals such as ruthenium, rhodium, palladium, osmium, iridium, and platinum are used extensively as catalysts In many cases, they offer the unique possibility of fast and atom-efficient, high hemo-, regio-, and enantioselective and high-yielded synthesis of desired chemical molecules under mild and often solvent-less reaction conditions. They offer the unique possibility of fast and atom-efficient, high hemo-, regio-, and enantioselective and high-yielded synthesis of desired chemical molecules under mild and often solvent-less reaction conditions These clean catalytic technologies play a key role in the drive towards environmentally benign processes with minimal waste generation (sustainable development, “green chemistry” concept) [1,2,3]. Green, clean, 100% atom-economic, Catalysts 2020, 10, 1409; doi:10.3390/catal10121409 www.mdpi.com/journal/catalysts
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