Highly Productive Synthesis of 1-Propenyloxybutan-1-ol Under Solvent-Free Homogeneous Ruthenium Catalyst Conditions

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

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process

Technological aspects of synthesis of poly(ethylene glycol) mono-1-propenyl ether monomers

For the first time, the technological aspects of the highly productive and selective synthesis of UV-reactive poly(ethylene glycol) mono-1-propenyl ether monomers was developed. The solvent-free isomerization of model commercial available 2-allyloxyethanol and allyloxypoly(ethylene glycol) derivatives, type Allyl–[OCH2CH2]n–OH, n = 1–5, into a 1-propenyl derivative under the homogeneous catalysis conditions using the ruthenium complexes were evaluated. The effect of a various reaction conditions (i.e. the concentration of [Ru] complex, the reaction temperature, reaction gas atmosphere) together with trace amounts of allyl hydroperoxides formed via autoxidation reaction of allyl substrates on the productivity of catalyst was examined in detail. Moreover, the significant role of the allyl substrate structures on the catalytic activity of ruthenium catalysts were also recognized. The optimal parameters of the scaled-up synthesis together with productivity of catalyst were first established