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Having been inspired by formose-based hypotheses surrounding the origin of life, we report on a novel catalytic route toward a series of recently discovered four-carbon α-hydroxy acids (AHA) and their esters from accessible and renewable glycolaldehyde (GA) in various solvents. The synthesis route follows a cascade type reaction network, and its mechanism with identification of the rate-determining step was investigated with in situ 13 C NMR. The mechanistic understanding led to optimized reaction conditions with higher overall rates of AHA formation by balancing Brønsted and Lewis acid activity, both originating from the tin halide catalyst. An optimal H + /Sn ratio of 3 was identified, and this number was surprisingly irrespective of the Sn oxidation state. Further rate enhancement was accomplished by adding small amounts of water to the reaction mixture, boosting the rate by a factor of 4.5 compared with pure methanol solvent. The cascade reaction selectively yields near 60% methyl-4-methoxy-2-hydroxybutanoate (MMHB). In the optimized rate regime in methanol, an initial TOF of 7.4 mol GA mol Sn −1 h −1 was found. In sterically hindered alcohols (isopropyl alcohol), the rate of AHA formation was even higher, and the corresponding vinyl glycolate esters arose as the main product. Vinyl glycolic acid, 2,4dihydroxybutanoic acid, and its lactone were formed significantly in nonprotic solvent. The corresponding AHAs have serious potential as building blocks in novel biobased polymers with tunable functionality. The incorporation of vinyl glycolic acid in polylactic acid-based polyesters is illustrated, and postmodification at the vinyl side groups indeed allows access to a range of properties, such as tunable hydrophilicity, which is otherwise difficult to attain for pure poly(L-lactic acid).

With the increasing use of laser sintering for the production of end-use parts, there is considerable interest in developing new and improved polymer materials for this technique. Due to the complexity of the process, however, materials are subject to very specific requirements in order to be easy processable. To gain a better understanding of these material requirements, this study investigates the currently most widely used material family: polyamides. Four commercial polyamide sintering grades, including two polyamide-12 grades, one polyamide-11 and one polyamide-6 grade, are characterized, using a new screening approach that encompasses all material properties essential for laser sintering. These include powder characteristics, melt flow, and solidification behavior of the polymer. The study reveals several particular characteristics of polyamides that explain the current popularity of this material family for laser sintering, and may be used as a guideline for finding new materials for the process.

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