Solid-state reactions using mechanochemical activation have emerged as solvent-free atom-efficient strategies for sustainable chemistry. Herein we report a new mechanochemical approach for the amide

Conversion of biobased platform chemicals to enantiopure compounds has become topical. We report a straightforward synthesis of 4-(acyloxy)-pentanoic acids from γ-valerolactone (GVL). An alkaline hydrolysis of GVL is followed by a stereoselective lipase-catalyzed acylation of the sodium salt. Acidic hydrolysis of the acylation product affords (R)-4-(acyloxy)­pentanoic acid and relactonized (S)-GVL. (R)-4-(Propionyloxy)­pentanoic acid and (R)-GVL are obtained with e.r. > 99/1. An additional enzymatic step following a slightly modified process affords (S)-4-(acetyloxy)­pentanoic acid with e.r. > 99/1. Simple access to enantiopure 4-(acyloxy)­pentanoic acids will stimulate the development of their novel applications, including biobased isotactic polymers.

No abstract

An expansion of the solvent‐free synthetic toolbox is essential for advances in the sustainable chemical industry. Mechanochemical reactions offer a superior safety profile and reduced amount of waste compared to conventional solvent‐based synthesis. Herein a new mechanochemical method was developed for nucleophilic substitution of alcohols using fluoro‐N,N,N′,N′‐tetramethylformamidinium hexafluorophosphate (TFFH) and K2HPO4 as an alcohol‐activating reagent and a base, respectively. Alcohol activation and reaction with a nucleophile were performed in one milling jar via reactive isouronium intermediates. Nucleophilic substitution with amines afforded alkylated amines in 31–91 % yields. The complete stereoinversion occurred for the SN2 reaction of (R)‐ and (S)‐ethyl lactates. Substitution with halide anions (F−, Br−, I−) and oxygen‐centered (CH3OH, PhO−) nucleophiles was also tested. Application of the method to the synthesis of active pharmaceutical ingredients has been demonstrated.

Solid-phase extraction that utilizes selective macrocyclic receptors can serve as a useful tool for removal of chemical wastes. Hemicucurbiturils are known to form inclusion complexes with suitably sized anions; however, their use in selective binding of non-charged species is still very limited. In this study, we found that cyclohexanohemicucurbit[8]uril encapsulates five- and six-membered sulfur- and oxygen-containing unsubstituted heterocycles, which is investigated by single-crystal X-ray diffraction, NMR spectroscopy, isothermal titration calorimetry, and thermogravimetry. The macrocycle acts as a promising selective sorption material for the extraction of sulfur heterocycles, such as 1,3-dithiolane and α-lipoic acid, from water.