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CO2 insertion reactions on terminal epoxides (styrene oxide, 1,2-epoxyhexane and butyl glycidyl ether) were performed in a binary homogeneous mixture comprising NaBr as the nucleophilic catalyst and diethylene glycol (DEG) as both solvent and catalyst activator (cation coordinating agent). The reaction protocol was initially studied under batch conditions either in autoclaves and glass reactors: quantitative formation of the cyclic organic carbonate products (COCs) were achieved at T=100 °C and p0(CO2)=1–40 bar. The process was then transferred to continuous-flow (CF) mode. The effects of the reaction parameters (T, p(CO2), catalyst loading, and flow rates) were studied using microfluidic reactors of capacities variable from 7.85 ⋅ 10−2 to 0.157 cm3. Albeit the CF reaction took place at T=220 °C and 120 bar, CF improved the productivity and allowed catalyst recycle through a semi-continuous extraction procedure. For the model case of 1,2-epoxyhexane, the (non-optimized) rate of formation of the corresponding carbonate, 4-butyl-1,3-dioxolan-2-one, was increased up to 27.6 mmol h−1 equiv.−1, a value 2.5 higher than in the batch mode. Moreover, the NaBr/DEG mixture was reusable without loss of performance for at least 4 subsequent CF-tests.

Multiple sustainable methodologies were developed for the chemical upgrading of HMF: i) at 30–90 °C, highly selective base-catalyzed acetylation and carboxymethylation reactions of HMF with nontoxic reagents as isopropenyl acetate (iPAc) and dimethyl carbonate (DMC) were achieved to prepare the corresponding ester and carbonate products, (5-formylfuran-2-yl)methyl acetate (5-formylfuran-2-yl) methyl carbonate, respectively; ii) based on the combined use of iPAc/DMC with acetone, a tandem protocol of acetylation/transcarbonation and aldol condensation was designed to synthesize a variety of HMF-derived α,β-unsaturated carbonyl compounds; iii) in water as a solvent, a chemoselective Pd-catalysed reductive amination of HMF with amino-alcohols also including glycerol derivatives, was developed using H2 at atmospheric pressure; iv) finally, both HMF and its ester and carbonate products successfully underwent Wittig vinylation reactions promoted by a methyl carbonate phosphonium salt ( [Ph3PCH3] [CH3OCO2]), to obtain the corresponding olefins. The vinylation reagent (the salt) was a DMC derivative. In all cases i-iv), not only processes occurred under mild conditions, but post-reaction procedures (work-up and purification) were optimized to isolate final products in high yields of 85–98%.

An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80&ndash, 90 &deg, C, both substrates were quantitatively converted into the corresponding amides through a catalyst-free N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30&ndash, 100 &deg, C and 1&ndash, 10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amide-acetal) products.

At 30 °C, in the presence of Amberlyst-15 as a catalyst, a tandem sequence was implemented by which a pool of innocuous reactants (isopropenyl acetate, acetic acid and acetone) allowed upgrading of glycerol through selective acetylation and acetalization processes. The study provided evidence for the occurrence of multiple concomitant reactions. Isopropenyl acetate acted as a transesterification agent to provide glyceryl esters, and it was concurrently subjected to an acidolysis reaction promoted by AcOH. Both these transformations co-generated acetone which converted glycerol into the corresponding acetals, while acidolysis sourced also acetic anhydride that acted as an acetylation reactant. However, tuning of conditions, mostly by changing the reactant molar ratio and optimizing the reaction time, was successful to steer the set of all reactions towards the synthesis of either a 1 : 1 mixture of acetal acetates (97% of which was solketal acetate) and triacetin, or acetal acetates in up to 91% yield, at complete conversion of glycerol. To the best of our knowledge, a one-pot protocol with such a degree of control on the functionalization of glycerol via transesterification and acetalization reactions has not been previously reported. The procedure was also easily reproduced on a gram scale, thereby proving its efficiency for preparative purposes. Finally, the design of experiments with isotopically labelled reagents, particularly d4-acetic acid and d6-acetone, helped to estimate the contribution of different reaction partners (iPAc/AcOH/acetone) to the formation of final products. This journal is

A new acid-catalyzed tandem sequence was investigated for the upgrading of renewable 1,2-diols such as propylene glycol (PG) and ethylene glycol (EG), with isopropenyl esters. For example, at 50 °C and in the presence of Amberlyst-15, the reaction of PG with nontoxic isopropenyl acetate allowed an initial irreversible monotransesterification of the diol, releasing acetone which then promoted acetalization on a second molecule of the glycol. The overall protocol was 100% carbon efficient, affording water as the sole byproduct. The reaction scope was extended to higher homologues of enol esters as isopropenyl-octanoate and phenylbutyrate. Additionally, the tandem sequence was successfully transferred in the continuous-flow (CF) mode where the catalyst (Amberlyst-15) could be used virtually indefinitely without loss of performance, and the solvent (THF or CPME) was quantitatively recovered and reused. Under CF conditions, the reaction of PG with isopropenyl acetate could be run at 30 °C and atmospheric pressure with a (nonoptimized) productivity up to 9.7 mmol gcat-1 h-1, 3 times higher than that achieved in the batch mode. When ethylene glycol was used, a lower tandem selectivity was observed due to predominance of transesterification products, mono- and diesters, over the acetal compound.