Robby Vroemans

The palladium-catalyzed Suzuki–Miyaura cross-coupling (SMC) reaction of organohalides and organoborons is a reliable carbon–carbon bond-forming method. This reaction involves a base-mediated transmetalation process, but the presence of a base also promotes competitive protodeborylation, which reduces the efficiency. Herein, we established a base-free SMC reaction via Lewis acid-mediated transmetalation of an organopalladium(II) intermediate with organoborons. Experimental and theoretical investigations indicate that the controlled release of the transmetalation-active intermediate enabled base-free transmetalation under heating conditions and enhanced the applicable scope of this process. This system enabled us to avoid the use of a base, and thus, rendered substrates with base-sensitive moieties available.

Molecules, Vol. 26, Pages 2937: 1,2,3-Triazoles as Biomimetics in Peptide Science

Molecules doi: 10.3390/molecules26102937

Authors: Naima Agouram El Mestafa El Hadrami Abdeslem Bentama

Natural peptides are an important class of chemical mediators, essential for most vital processes. What limits the potential of the use of peptides as drugs is their low bioavailability and enzymatic degradation in vivo. To overcome this limitation, the development of new molecules mimicking peptides is of great importance for the development of new biologically active molecules. Therefore, replacing the amide bond in a peptide with a heterocyclic bioisostere, such as the 1,2,3-triazole ring, can be considered an effective solution for the synthesis of biologically relevant peptidomimetics. These 1,2,3-triazoles may have an interesting biological activity, because they behave as rigid link units, which can mimic the electronic properties of amide bonds and show bioisosteric effects. Additionally, triazole can be used as a linker moiety to link peptides to other functional groups.

On the path to finding better catalysts for polyolefin plastic waste conversion to aromatics, we have found that a waste refinery catalyst performed better than the fresh catalyst with decreased accumulation of deactivating carbonaceous deposits. Fluorescence microscopy and vibrational spectroscopy has been used to elucidate the interaction of the polymer with the catalyst and to map the location and type of bulky aromatic species.

Abstract

Polypropylene (PP) makes up a large share of our plastic waste. We investigated the conversion of PP over the industrial Fluid Catalytic Cracking catalyst (FCC-cat) used to produce gasoline from crude oil fractions. We studied transport limitations arising from the larger size of polymers compared to the crude oil-based feedstock by testing the components of this catalyst separately. Infrared spectroscopy and confocal fluorescence microscopy revealed the role of the FCC matrix in aromatization, and the zeolite Y domains in coking. An equilibrium catalyst (ECAT), discarded during FCC operation as waste, produced the same aromatics content as a fresh FCC-cat, while coking decreased significantly, likely due to the reduced accessibility and activity of the zeolite domains and an enhanced cracking activity of the matrix due to metal deposits present in ECAT. This mechanistic understanding provides handles for further improving the catalyst composition towards higher aromatics selectivity.

Molecules, Vol. 26, Pages 2846: Stereocomplex Polylactide for Drug Delivery and Biomedical Applications: A Review

Molecules doi: 10.3390/molecules26102846

Authors: Seung Hyuk Im Dam Hyeok Im Su Jeong Park Justin Jihong Chung Youngmee Jung Soo Hyun Kim

Polylactide (PLA) is among the most common biodegradable polymers, with applications in various fields, such as renewable and biomedical industries. PLA features poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) enantiomers, which form stereocomplex crystals through racemic blending. PLA emerged as a promising material owing to its sustainable, eco-friendly, and fully biodegradable properties. Nevertheless, PLA still has a low applicability for drug delivery as a carrier and scaffold. Stereocomplex PLA (sc-PLA) exhibits substantially improved mechanical and physical strength compared to the homopolymer, overcoming these limitations. Recently, numerous studies have reported the use of sc-PLA as a drug carrier through encapsulation of various drugs, proteins, and secondary molecules by various processes including micelle formation, self-assembly, emulsion, and inkjet printing. However, concerns such as low loading capacity, weak stability of hydrophilic contents, and non-sustainable release behavior remain. This review focuses on various strategies to overcome the current challenges of sc-PLA in drug delivery systems and biomedical applications in three critical fields, namely anti-cancer therapy, tissue engineering, and anti-microbial activity. Furthermore, the excellent potential of sc-PLA as a next-generation polymeric material is discussed.

Molecules, Vol. 26, Pages 2840: The Hydrolysis of Phosphinates and Phosphonates: A Review

Molecules doi: 10.3390/molecules26102840

Authors: Nikoletta Harsági György Keglevich

Phosphinic and phosphonic acids are useful intermediates and biologically active compounds which may be prepared from their esters, phosphinates and phosphonates, respectively, by hydrolysis or dealkylation. The hydrolysis may take place both under acidic and basic conditions, but the C-O bond may also be cleaved by trimethylsilyl halides. The hydrolysis of P-esters is a challenging task because, in most cases, the optimized reaction conditions have not yet been explored. Despite the importance of the hydrolysis of P-esters, this field has not yet been fully surveyed. In order to fill this gap, examples of acidic and alkaline hydrolysis, as well as the dealkylation of phosphinates and phosphonates, are summarized in this review.

Journal of Porphyrins and Phthalocyanines, Volume 26, Issue 06n07, Page 427-433, June & July 2022.
A facile synthetic strategy was developed for the synthesis of meso -tetrakis(4-formyl-phenyl)porphyrin and meso -tetrakis(3-formylphenyl)porphyrin from commercially available starting materials. This method gives facile access to practical amounts of these synthons in high purity and good overall yield, without employing laborious chromatographic separations. The reduction of the respective carboxylic acid-functionalized porphyrins by LiAlH4 afforded the tetra(benzylalcohol)porphyrin intermediates, subsequently utilized in a Parikh-Doering oxidation to selectively afford the desired tetraformylated products. The inherent ease of synthesis of these porphyrin building blocks provides a convenient pathway for the synthesis of various macromolecular and supramolecular architectures for applied chemical technologies.

Nature Reviews Chemistry, Published online: 07 May 2021; doi:10.1038/s41570-021-00286-1

As scientists of all stripes grow as leaders, it becomes their responsibility to shed light on the opportunities that may be hidden within an apparent failure. Presented as a letter to his younger self, Marc Reid looks back at the time when he could scarcely handle professional rejection and examines the lessons he learned.

Conditions for the direct mono‐ or di‐arylation of 2‐benzyl‐1,2,3‐triazole using phosphine‐free Pd(OAc)₂ catalyst are described. This C−H arylation method was applied to the easy synthesis of π‐extended phenanthro[9,10‐d][1,2,3]triazoles.

Abstract

The reactivity of 2‐benzyl‐1,2,3‐triazole in palladium‐catalyzed direct arylation was studied. The reaction conditions for the selective synthesis of 2‐benzyl‐4‐aryl‐1,2,3‐triazoles in moderate to high yields using phosphine‐free Pd(OAc)₂ catalyst and inexpensive KOAc base have been found. Then, from these 4‐aryl‐1,2,3‐triazoles, the palladium‐catalyzed C−H bond functionalization of the C5‐position allowed the synthesis of the corresponding 4,5‐diarylated 2‐benzyl‐1,2,3‐triazoles. This selective 4,5‐diarylation of 2‐benzyl‐1,2,3‐triazole was successfully applied for the straightforward building of the π‐extended polycyclic heteroaromatic structures phenanthro[9,10‐d][1,2,3]triazoles through Pd‐catalyzed C4‐ and C5‐intermolecular arylations followed by Pd‐catalyzed C−H intramolecular arylation.