Theoretical Insights into the Mechanism and Origin of Solvent-Dependent Selectivity in the Cyclization of Propargyl Alcohols for the Divergent Synthesis of N-Heterocycles.

This study elucidates the mechanisms and principles governing chemoselectivity in synthesizing two distinct N-heterocycles, benzimidazole thiazine and benzothiazole imidazole, through BF3•OEt2-catalyzed cyclization reactions of propargyl alcohols with benzimidazole thiols. Employing density functional theory calculations, we highlight the crucial role of fluorine source in influencing chemoselectivity. In DCM, BF3, as the catalytic center, coordinates with propargyl alcohol's hydroxyl group to form a precursor. Conversely, in DMF, [BF2•DMF]+, formed from DMF and BF3•OEt2, acts as the catalytic center, activating the propargyl alcohol's hydroxyl group. The mechanisms in both solvents involve sequential steps: B-O bond formation, C-O bond cleavage, S-C bond formation, hydrogen atom transfer (HAT), cyclization, and deprotonation. A notable difference is the HAT process: in DCM, it follows a 1,5-HAT process, while in DMF, BF4- formation from DMF and BF3•OEt2 provides a fluorine source and introduces steric hindrance, favoring a 1,6-HAT process and leading to unique chemoselectivity. This pioneering research showcases the impact of DMF on cyclization reactions, offering valuable insights for comprehending and designing reactions driven by fluorine sources. Crucially, our results propose an innovative reaction mechanism featuring lower potential energy surfaces, enhancing our understanding of the intricate interplay among reactants, catalysts, and solvents.

Effectiveness of postoperative superficial radiotherapy following the keloid-cross-flap surgery for auricular keloid: A prospective cohort study.

BACKGROUND AND PURPOSE: Retaining partial keloid skin to make cross flaps (keloid-cross-flap surgery) is a modification of the core excision. This study aimed to compare the effectiveness of superficial radiotherapy versus compression therapy after keloid-cross-flap surgery. MATERIALS AND METHODS: In this prospective cohort study, auricular keloid patients were consecutively screened from January 2019 to December 2021. They underwent keloid-cross-flap surgery and then enter either the superficial radiotherapy or the compression treatment group. The primary outcome was the one-year keloid recurrence rate. Secondary outcomes included: non-completion rate of adjuvant treatment; Patient and Observer Scar Assessment Scale (POSAS) scores and auricular aesthetics scores, evaluated by a four-point Likert scale (1 = poor to 4 = excellent) of non-recurring patients. Propensity score matching (PSM) was used to eliminate potential confounding factors. RESULTS: 123 patients were included in the superficial radiotherapy group and 128 in the compression treatment group. Non-completion rate was significantly higher in the compression treatment group (17.97 %), while the loss rate was comparable between the two groups. Overall, 13 patients (13.54 %) relapsed in superficial radiotherapy group, while 22 patients (25.58 %) in compression group (p < 0.05). After PSM, 59 patients in each group were analyzed, and the recurrence rate was lower in the superficial radiotherapy group (13.56 %). Of relapse-free patients, no significant difference was found in PSAS scores, OSAS scores or aesthetic scores between the two groups. CONCLUSION: Keloid-cross-flap surgery could provide favorable morphologic repair of the auricular keloid, and postoperative superficial radiotherapy shows higher compliance and lower recurrence rate comparing to compression treatment.

Iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer and hydrogen atom transfer.

Site selective functionalization of inert remote C(sp3)-H bonds to increase molecular complexity offers vital potential for chemical synthesis and new drug development, thus it has been attracting ongoing research interest. In particular, typical ß-C(sp3)-H arylation methods using chelation-assisted metal catalysis or metal-catalyzed oxidative/photochemical in situ generated allyl C(sp3)-H bond processes have been well developed. However, radical-mediated direct ß-C(sp3)-H arylation of carbonyls remains elusive. Herein, we describe an iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer (XAT) and hydrogen atom transfer (HAT). The method involves diethylaminoethyl radical-mediated generation of an aryl radical intermediate via XAT, then directed 1,5-HAT to form the remote alkyl radical intermediate and radical-radical coupling with cyanoarenes, and is applicable to a broad scope of unactivated remote C(sp3)-H bonds like ß-C(sp3)-H bonds of o-iodoaryl-substituted alkanones and α-C(sp3)-H bonds of o-iodoarylamides. Experimental findings are supported by computational studies (DFT calculations), revealing that this method operates via a radical-relay stepwise mechanism involving multiple SET, XAT, 1,5-HAT and radical-radical coupling processes.

Advancements in tissue engineering for articular cartilage regeneration.

Articular cartilage injury is a prevalent clinical condition resulting from trauma, tumors, infection, osteoarthritis, and other factors. The intrinsic lack of blood vessels, nerves, and lymphatic vessels within cartilage tissue severely limits its self-regenerative capacity after injury. Current treatment options, such as conservative drug therapy and joint replacement, have inherent limitations. Achieving perfect regeneration and repair of articular cartilage remains an ongoing challenge in the field of regenerative medicine. Tissue engineering has emerged as a key focus in articular cartilage injury research, aiming to utilize cultured and expanded tissue cells combined with suitable scaffold materials to create viable, functional tissues. This review article encompasses the latest advancements in seed cells, scaffolds, and cytokines. Additionally, the role of stimulatory factors including cytokines and growth factors, genetic engineering techniques, biophysical stimulation, and bioreactor systems, as well as the role of scaffolding materials including natural scaffolds, synthetic scaffolds, and nanostructured scaffolds in the regeneration of cartilage tissues are discussed. Finally, we also outline the signaling pathways involved in cartilage regeneration. Our review provides valuable insights for scholars to address the complex problem of cartilage regeneration and repair.