1,720,974 research outputs found
Bis-pyrrolidone structures as versatile building blocks for the synthesis of bio-based polyesters and for the preparation of additives
No full textIn this work, three bis-pyrrolidone-based structures (BP) were synthesized combining dimethyl itaconate (DMI), the dimethyl ester derivative of itaconic acid, with various aliphatic diamines having a C4 to C12 carbon chain length with the aim of developing novel bio-based building blocks. All three BPs were obtained with a purity >93% and could further be used without performing any tedious purification step, therefore allowing an easy scalability of the synthesis on a 10 g scale. Their potential application was demonstrated in two key areas of modern polymer science: (1) the enzymatic synthesis of polyesters and (2) their use as poly(lactic acid) (PLA) additives. Firstly, the possibility of obtaining oligoesters by reacting the BP monomers with various aliphatic diols in a solventless reaction system and under mild conditions (T < 90 °C) was demonstrated thanks to the use of enzymatic catalysis. Linear oligoesters having mean average molecular weights between 1000 g mol−1 and 6100 g mol−1 and dispersity values <2 were successfully obtained. When applying the BP structures as PLA additives, the incorporation of a 10% w w−1 BP in the polyester matrix resulted in systems with an 8× increased elongation at break and a decrease in the glass transition temperature compared to the neat polymer matrix
MULTICOMPONENT SYNTHESIS OF VARIOUS DIHYDROBENZOXAZEPINONES THROUGH UGI AND MITSUNOBU REACTIONS
No full textStudio della stereochimica dell’acido vanilmandelico mediante tecniche di cromatografia liquida accoppiata alla spettrometria di massa
No full textThioisomunchnones derivatives of mandelic acid and vanilmandelic acid : a serendipitous discovery with interesting applications
No full textEnantiospecific and Diastereoselective Synthesis of 4,4-Disubstituted-3-amino-2-azetidinones, Starting from D-Serine
No full textOn the effect of microwave energy on the Michael addition of dimethyl malonate on levoglucosenone
No full textAmong biomass-derived platform molecules one of the most prominent structures is levoglucosenone (LGO) from which it is possible to derive a wide array of solvents, chemicals, and polymeric materials. In this work we investigated the Michael addition of dimethyl malonate on levoglucosenone by testing several alternative catalysts ranging from Lewis acids to structured silicas and clays. The work had the double aim to i) optimize the reaction using the widely reported KF/Alumina catalyst, giving a frame of reference for its relative activity in this Michael addition and ii) conduct a catalyst screen while investigating various reaction mechanisms. Among the tested catalysts, Ca(OH)2 was the best candidate to substitute KF/Alumina, reaching yields >90 % after only 5 min of microwave irradiation
A Chemoenzymatic Route to New Chiral Isocyanides and Their Use in Highly Diastereoselective Ugi Reactions
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ASYMMETRIC SYNTHESIS OF 4,4-DISUBSTITUTED BETA-LACTAMS VIA STEREOCONTROLLED ADDITION OF ORGANOMETALS TO KETONES DERIVED FROM D-SERINE
No full textThe homo-PADAM Protocol: Stereoselective and Operationally Simple Synthesis of alpha-Oxo or alpha-Hydroxy-gamma-acylaminoamides and Chromanes
No full textA straightforward and fully stereoselective synthesis of a new class of peptidomimetics, that is alpha-oxo-gamma-acylaminoamides, was achieved starting from various benzaldehydes by a sequence of 1) an asymmetric organocatalytic Mannich reaction, 2) a Passerini multicomponent reaction, 3) an amine deprotection–acyl migration protocol, and 4) a final oxidation. The whole sequence can be performed without purification of the intermediates and represents the first example of a homo-Passerini– amine deprotection–acyl migration (PADAM) strategy. Highly stereoselective reduction of the alpha-oxo-gamma-acylaminoamides afforded alpha-hydroxy-gamma-acylaminoamides as well. In some cases both diastereomers were obtained by simply changing the reducing agent. Finally, starting from protected salicylaldehyde, the same sequence, followed by a Mitsunobu cyclization, afforded highly substituted chromanes
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