Remote-Controlled Exchange Rates by Photoswitchable Internal Catalysis of Dynamic Covalent Bonds.

The transesterification rate of boronate esters with diols is tunable over 14 orders of magnitude. Rate acceleration is achieved by internal base catalysis, which lowers the barrier for proton transfer. Here we report a photoswitchable internal catalyst that tunes the rate of boronic ester/diol exchange over 4 orders of magnitude. We employed an acylhydrazone molecular photoswitch, which forms a thermally stable but photoreversible intramolecular H-bond, to gate the activity of the internal base catalyst in 8-quinoline boronic ester. The photoswitch is bidirectional and can be cycled repeatedly. The intramolecular H-bond is found to be essential to the design of this photoswitchable internal catalyst, as protonating the quinoline with external sources of acid has little effect on the exchange rate.

Catalytic, Enantioselective ß-Protonation through a Cooperative Activation Strategy.

The NHC-catalyzed transformation of unsaturated aldehydes into saturated esters through an organocatalytic homoenolate process has been thoroughly studied. Leveraging a unique "Umpolung"-mediated ß-protonation, this process has evolved from a test bed for homoenolate reactivity to a broader platform for asymmetric catalysis. Inspired by our success in using the ß-protonation process to generate enals from ynals with good E/Z selectivity, our early studies found that an asymmetric variation of this reaction was not only feasible, but also adaptable to a kinetic resolution of secondary alcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach through inclusion of a hydrogen bond donor cocatalyst significantly improved enantioselectivity.

Mechanism of Copper(I)-Catalyzed 5-Iodo-1,2,3-triazole Formation from Azide and Terminal Alkyne.

5-Iodo-1,2,3-triazole (iodotriazole) can be prepared from a copper(I)-catalyzed reaction between azide and terminal alkyne in the presence of an iodinating agent, with 5-protio-1,2,3-triazole (protiotriazole) as the side product. The increasing utilities of iodotriazoles in synthetic and supramolecular chemistry drive the efforts in improving their selective syntheses based on a sound mechanistic understanding. A routinely proposed mechanism takes the cue from the copper(I)-catalyzed azide-alkyne cycloaddition, which includes copper(I) acetylide and triazolide as the early and the late intermediates, respectively. Instead of being protonated to afford protiotriazole, an iodinating agent presumably intercepts the copper(I) triazolide to give iodotriazole. The current work shows that copper(I) triazolide can be iodinated to afford iodotriazoles. However, when the reaction starts from a terminal alkyne as under the practical circumstances, 1-iodoalkyne (iodoalkyne) is an intermediate while copper(I) triazolide is bypassed on the reaction coordinate. The production of protiotriazole commences after almost all of the iodoalkyne is consumed. Using (1)H NMR to follow a homogeneous iodotriazole forming reaction, the rapid formation of an iodoalkyne is shown to dictate the selectivity of an iodotriazole over a protiotriazole. To ensure the exclusive production of iodotriazole, the complete conversion of an alkyne to an iodoalkyne has to, and can be, achieved at the early stage of the reaction.

Infective Endocarditis Secondary to Needle Embolization to the Heart: A Case Report.

This case report explores the rare occurrence of a needle embolism in the heart among individuals with intravenous drug use (IVDU). The intricate symptomatology, ranging from overt chest pain to asymptomatic cases, poses diagnostic challenges and may lead to underrecognition. Healthcare professionals must navigate varied presentations, emphasizing the need for a nuanced diagnostic approach. The interplay of needle embolisms with infective endocarditis and sepsis adds complexity, requiring a comprehensive understanding. Ongoing education and training are crucial for healthcare professionals to address the evolving challenges of needle embolism management within the broader context of infective endocarditis and sepsis. Our patient is a 31-year-old female with a history of IVDU who presented with heart palpitations and shortness of breath. A CT scan revealed lung lesions and a needle in the right ventricle. The patient was admitted for methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia, where she underwent video-assisted thoracoscopic surgery (VATS) involving empyemectomy and wedge resection of the right-middle and lower lobes. However, it was deemed very risky to remove the needle from the right ventricle. Despite extensive discussion and patient education, she left the rehabilitation center without follow-up, highlighting the challenges of managing IV drug-related complications. In conclusion, heightened awareness and a proactive approach are crucial in managing rare complications such as needle embolisms in IVDU patients. This case underscores the significance of staying informed to improve patient care and outcomes amid evolving healthcare practices.