Selective etherification of beta-citronellene catalyzed by zeolite beta

The etherification of beta-citronellene with bioalcohols over zeolite beta was performed in a continuous flow liquid phase reactor. At 80 degrees C, the catalyst exhibits 50% beta-citronellene conversion with a high selectivity for the etherification reaction. High chemoselectivity (90%) at the beta-double bond of beta-citronellene was observed, while beta-citronellene isomers were formed as minor products. In order to rationalize the observed chemoselectivity, the relative stabilities of the protonated reaction intermediates were estimated using theoretical calculations. The zeolite beta catalyst exhibits high stability as well as low coke formation. Considering the industrial importance of terpene ethers as sophisticated solvents, fragrance or flavor additives, a novel and environmentally friendly synthesis is presented as an alternative to homogeneous catalysis using strong Bronsted or Lewis acids in solution

Regioselective etherification of b-citronellene catalyzed by zeolite beta

The etherification of beta-citronellene with bioalcohols over zeolite beta was performed in a continuous flow liquid phase reactor. At 80 degrees C, the catalyst exhibits 50% beta-citronellene conversion with a high selectivity for the etherification reaction. High chemoselectivity (90%) at the beta-double bond of beta-citronellene was observed, while beta-citronellene isomers were formed as minor products. In order to rationalize the observed chemoselectivity, the relative stabilities of the protonated reaction intermediates were estimated using theoretical calculations. The zeolite beta catalyst exhibits high stability as well as low coke formation. Considering the industrial importance of terpene ethers as sophisticated solvents, fragrance or flavor additives, a novel and environmentally friendly synthesis is presented as an alternative to homogeneous catalysis using strong Bronsted or Lewis acids in solution

One-dimensional supramolecular surface structures: 1,4-diisocyanobenzene on Au(111) surfaces

One-dimensional supramolecular structures formed by adsorbing low coverages of 1,4-diisocyanobenzene on Au(111) at room temperature are obtained and imaged by scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. The structures originate from step edges or surface defects and arrange predominantly in a straight fashion on the substrate terraces along the 〈11-0〉 directions. They are proposed to consist of alternating units of 1,4-diisocyanobenzene molecules and gold atoms with a unit cell in registry with the substrate corresponding to four times the lattice interatomic distance. Their long 1-D chains and high thermal stability offer the potential to use them as conductors in nanoelectronic applications. © the Owner Societies

Poly(2-alkyl-2-oxazoline)s: A polymer platform to sustain the release from tablets with a high drug loading

Sustaining the release of highly dosed APIs from a matrix tablet is challenging. To address this challenge, this study evaluated the performance of thermoplastic poly (2-alkyl-2-oxazoline)s (PAOx) as matrix excipient to produce sustained-release tablets via three processing routes: (a) hot-melt extrusion (HME) combined with injection molding (IM), (b) HME combined with milling and compression and (c) direct compression (DC). Different PAOx (co-)polymers and polymer mixtures were processed with several active pharmaceutical ingredients having different aqueous solubilities and melting temperatures (metoprolol tartrate (MPT), metformin hydrochloride (MTF) and theophylline anhydrous (THA)). Different PAOx grades were synthesized and purified by the Supramolecular Chemistry Group, and the effect of PAOx grade and processing technique on the in vitro release kinetics was evaluated. Using the hydrophobic poly (2-n-propyl-2-oxazoline) (P(n)PrOx) as a matrix excipient allowed to sustain the release of different APIs, even at a 70% (w/w) drug load. Whereas complete THA release was not achieved from the P(n)PrOx matrix over 24 ​h regardless of the processing technique, adding 7.5% w/w of the hydrophilic poly (2-ethyl-2-oxazoline) to the hydrophobic P(n)PrOx matrix significantly increased THA release, highlighting the relevance of mixing different PAOx grades. In addition, it was demonstrated that the release of THA was similar from co-polymer and polymer mixtures with the same polymer ratios. On the other hand, as the release of MTF from a P(n)PrOx matrix was fast, the more hydrophobic poly (2-sec-butyl-2-oxazoline) (P(sec)BuOx) was used to retard MTF release. In addition, a mixture between the hydrophilic PEtOx and the hydrophobic P(sec)BuOx allowed accurate tuning of the release of MTF formulations. Finally, it was demonstrated that PAOx also showed a high ability to tune the in vivo release. IM tablets containing 70% MTF and 30% P(sec)BuOx showed a lower in vivo bioavailability compared to IM tablets containing a low PEtOx concentration (7.5%, w/w) in combination with P(sec)BuOx (22.5%, w/w). Importantly, the in vivo MTF blood level from the sustained release tablets correlated well with the in vitro release profiles. In general, this work demonstrates that PAOx polymers offer a versatile formulation platform to adjust the release rate of different APIs, enabling sustained release from tablets with up to 70% w/w drug loading

Synthesis of Seven-Membered Ring Ethers and Lactones

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