Comparing cefazolin/ metronidazole, piperacillin-tazobactam, or c efoxitin as surgical antibiotic prophylaxis in patients undergoing pancreaticoduodenectomy: A retrospective cohort study.

BACKGROUND: Preoperative antibiotic options for pancreaticoduodenectomy (PD) include cefoxitin (CX), piperacillin-tazobactam (PT), or combined cefazolin and metronidazole (CM). Recent studies suggest the superiority of PT over CX, but evidence for CM is unclear. OBJECTIVE: To explore the impact of preoperative antibiotic selection (CM vs. PT and CX vs. PT) on the development of surgical site infections (SSI). METHODS: Consecutive adult patients at one institution who underwent PD from November 2017 to December 2021 and received either CM, PT, or CX preoperatively, were included. The primary outcome was SSI. Secondary outcomes included postoperative infections and clinically significant postoperative pancreatic fistula (POPF). Logistic regression models were used. RESULTS: Among 127 patients included in the study, PT, CM, and CX were administered in 46 (36.2%), 44 (34.6%), and 37 (29.4%) patients, respectively. There were 32 (27.1%) SSI, 20 (36.1%) infections, and 21 (22.9%) POPF events. PT use was associated with reduced risk of SSI compared to CX (OR: 0.32, 95% CI: 0.11-0.89, p = 0.03), but there was no difference as compared to CM (OR: 0.75, 95% CI: 0.27-2.13, p = 0.59). There were no differences in secondary outcomes. CONCLUSION: PT reduced SSI rates compared to CX but was no different to CM among patients undergoing PD at our center.

Quality of life following perioperative optimization with nutritional supplements in patients undergoing gastrointestinal surgery for cancer: A randomized, placebo-controlled feasibility clinical trial.

BACKGROUND: Up to two thirds of patients presenting for abdominal cancer surgery are malnourished pre-operatively. Perioperative nutritional supplementation has been proposed to improve surgical outcomes, though its effect on quality of life (QoL) is not yet understood. METHODS: A randomized controlled feasibility trial for perioperative nutrition among patients undergoing major abdominal cancer surgery was conducted. Participants in the intervention group received supplements for 30 days before surgery. Participants completed two QoL questionnaires (EORTC-QLQ-C-30 and FACT-G) at baseline, then 4 and 12 weeks postoperatively. Participants were compared between and within groups at baseline, Weeks 4, and 12 using t tests. Minimal clinically important differences (MCIDs) were considered as a 10-point worsening from baseline. RESULTS: Sixty-six participants were available for analysis in this study, including 33 in the intervention and 30 in the control arms. Baseline demographics were balanced between groups except for different rates of pancreas cancer (36% intervention vs. 9% control) and colorectal cancer (19% intervention vs. 34% control). At baseline, participants in the intervention group had lower overall QoL (59% vs. 77%, p = 0.01), role functioning (72% vs 88%, p = 0.045), and cognitive functioning (79% vs 90%, p = 0.047). Following surgery, role and physical functioning worsened in the control group, without significant differences between groups. Role functioning was persistently worsened at 12 weeks in the control group. The rates of MCIDs were similar between both intervention and control groups. DISCUSSION: Perioperative nutrition was associated with preservation of QoL in the postoperative period following major abdominal cancer surgery compared to placebo. SUMMARY: Among patients undergoing surgery for cancer, the majority present at high risk for malnutrition. In this placebo-controlled randomized trial among patients undergoing major abdominal surgery for cancer, preoperative nutrition supplementation was associated with the preservation of QoL in the postoperative period.

Robotic versus Laparoscopic Liver Resection in Various Settings: An International Multicenter Propensity Score Matched Study of 10.075 Patients.

OBJECTIVE: The aim of this study was to compare the perioperative outcomes of robotic liver surgery (RLS) and laparoscopic liver surgery (LLS) in various settings. SUMMARY BACKGROUND DATA: Clear advantages of RLS over LLS have rarely been demonstrated, and the associated costs of robotic surgery are generally higher than those of laparoscopic surgery. Therefore, the exact role of the robotic approach in minimally invasive liver surgery remains to be defined. METHODS: In this international retrospective cohort study, the outcomes of patients who underwent RLS and LLS for all indications between 2009 and 2021 in 34 hepatobiliary referral centers were compared. Subgroup analyses were performed to compare both approaches across several types of procedures: minor resections in the anterolateral (2, 3, 4b, 5, and 6) or posterosuperior segments (1, 4a, 7, 8), and major resections (≥3 contiguous segments). Propensity score matching (PSM) was used to mitigate the influence of selection bias. The primary outcome was textbook outcome in liver surgery (TOLS), previously defined as the absence of intraoperative incidents ≥grade 2, postoperative bile leak ≥grade B, severe morbidity, readmission, and 90-day or in-hospital mortality with the presence of an R0 resection margin in case of malignancy. The absence of a prolonged length of stay was added to define TOLS+. RESULTS: Among the 10.075 included patients, 1.507 underwent RLS and 8.568 LLS. After PSM, both groups constituted 1.505 patients. RLS was associated with higher rates of TOLS (78.3% vs. 71.8%, P<0.001) and TOLS+ (55% vs. 50.4%, P=0.026), less Pringle usage (39.1% vs. 47.1%, P<0.001), blood loss (100 vs. 200 milliliters, P<0.001), transfusions (4.9% vs. 7.9%, P=0.003), conversions (2.7% vs 8.8%, P<0.001), overall morbidity (19.3% vs. 25.7%, P<0.001) and R0 resection margins (89.8% vs. 86%, P=0.015), but longer operative times (190 vs. 210 min, P=0.015). In the subgroups, RLS tended to have higher TOLS rates, compared to LLS, for minor resections in the posterosuperior segments (n=431 per group, 75.9% vs. 71.2%, P=0.184) and major resections (n=321 per group, 72.9% vs. 67.5%, P=0.086), although these differences did not reach statistical significance. CONCLUSIONS: While both producing excellent outcomes, RLS might facilitate slightly higher TOLS rates than LLS.

Circumstances and implications of conversion from minimally invasive to open liver resection: a multi-center analysis from the AMILES registry.

BACKGROUND: Minimally invasive approaches to liver resection (MILR) are associated with favorable outcomes. The aim of this study was to determine the implications of conversion to an open procedure on perioperative outcomes. METHODS: Patients who underwent MILR at 10 North American institutions were identified from the Americas Minimally Invasive Liver Resection (AMILES) database. Outcomes of patients who required conversion were compared to those who did not. Additionally, outcomes after conversion due to unfavorable findings (poor visualization/access, lack of progress, disease extent) versus intraoperative events (bleeding, injury, cardiopulmonary instability) were compared. RESULTS: Of 1675 patients who underwent MILR, 102 (6.1%) required conversion. Conversion rate ranged from 4.4% for left lateral sectionectomy to 10% for right hepatectomy. The primary reason for conversion was unfavorable findings in 67 patients (66%) and intraoperative adverse events in 35 patients (34%). By multivariable analysis, major resection, cirrhosis, prior liver surgery, and tumor proximity to major vessels were identified as risk factors for conversion (p < 0.05). Patients who required conversion had higher blood loss, transfusion requirements, operative time, and length of stay, (p < 0.05). They also had higher major complication rates (23% vs. 5.2%, p < 0.001) and 30-day mortality (8.8% vs. 1.3%, p < 0.001). When compared to those who required conversion due to unfavorable findings, patients who required conversion due to intraoperative adverse events had significantly higher major complication rates (43% vs. 14%, p = 0.012) and 30-day mortality (20% vs. 3.0%, p = 0.007). CONCLUSIONS: Conversion from MILR to open surgery is associated with increased perioperative morbidity and mortality. Conversion due to intraoperative adverse events is rare but associated with significantly higher complication and mortality rates, while conversion due to unfavorable findings is associated with similar outcomes as planned open resection. High-risk patients may benefit from early conversion in a controlled fashion if difficulties are encountered or anticipated.

Incidence of Diabetes in Children and Adolescents During the COVID-19 Pandemic: A Systematic Review and Meta-Analysis.

Importance: There are reports of increasing incidence of pediatric diabetes since the onset of the COVID-19 pandemic. Given the limitations of individual studies that examine this association, it is important to synthesize estimates of changes in incidence rates. Objective: To compare the incidence rates of pediatric diabetes during and before the COVID-19 pandemic. Data Sources: In this systematic review and meta-analysis, electronic databases, including Medline, Embase, the Cochrane database, Scopus, and Web of Science, and the gray literature were searched between January 1, 2020, and March 28, 2023, using subject headings and text word terms related to COVID-19, diabetes, and diabetic ketoacidosis (DKA). Study Selection: Studies were independently assessed by 2 reviewers and included if they reported differences in incident diabetes cases during vs before the pandemic in youths younger than 19 years, had a minimum observation period of 12 months during and 12 months before the pandemic, and were published in English. Data Extraction and Synthesis: From records that underwent full-text review, 2 reviewers independently abstracted data and assessed the risk of bias. The Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guideline was followed. Eligible studies were included in the meta-analysis and analyzed with a common and random-effects analysis. Studies not included in the meta-analysis were summarized descriptively. Main Outcomes and Measures: The primary outcome was change in the incidence rate of pediatric diabetes during vs before the COVID-19 pandemic. The secondary outcome was change in the incidence rate of DKA among youths with new-onset diabetes during the pandemic. Results: Forty-two studies including 102 984 incident diabetes cases were included in the systematic review. The meta-analysis of type 1 diabetes incidence rates included 17 studies of 38 149 youths and showed a higher incidence rate during the first year of the pandemic compared with the prepandemic period (incidence rate ratio [IRR], 1.14; 95% CI, 1.08-1.21). There was an increased incidence of diabetes during months 13 to 24 of the pandemic compared with the prepandemic period (IRR, 1.27; 95% CI, 1.18-1.37). Ten studies (23.8%) reported incident type 2 diabetes cases in both periods. These studies did not report incidence rates, so results were not pooled. Fifteen studies (35.7%) reported DKA incidence and found a higher rate during the pandemic compared with before the pandemic (IRR, 1.26; 95% CI, 1.17-1.36). Conclusions and Relevance: This study found that incidence rates of type 1 diabetes and DKA at diabetes onset in children and adolescents were higher after the start of the COVID-19 pandemic than before the pandemic. Increased resources and support may be needed for the growing number of children and adolescents with diabetes. Future studies are needed to assess whether this trend persists and may help elucidate possible underlying mechanisms to explain temporal changes.

Minimally Invasive Versus Open Liver Resections for Hepatocellular Carcinoma in Patients With Metabolic Syndrome.

OBJECTIVE: To compare minimally invasive (MILR) and open liver resections (OLRs) for hepatocellular carcinoma (HCC) in patients with metabolic syndrome (MS). BACKGROUND: Liver resections for HCC on MS are associated with high perioperative morbidity and mortality. No data on the minimally invasive approach in this setting exist. MATERIAL AND METHODS: A multicenter study involving 24 institutions was conducted. Propensity scores were calculated, and inverse probability weighting was used to weight comparisons. Short-term and long-term outcomes were investigated. RESULTS: A total of 996 patients were included: 580 in OLR and 416 in MILR. After weighing, groups were well matched. Blood loss was similar between groups (OLR 275.9±3.1 vs MILR 226±4.0, P =0.146). There were no significant differences in 90-day morbidity (38.9% vs 31.9% OLRs and MILRs, P =0.08) and mortality (2.4% vs 2.2% OLRs and MILRs, P =0.84). MILRs were associated with lower rates of major complications (9.3% vs 15.3%, P =0.015), posthepatectomy liver failure (0.6% vs 4.3%, P =0.008), and bile leaks (2.2% vs 6.4%, P =0.003); ascites was significantly lower at postoperative day 1 (2.7% vs 8.1%, P =0.002) and day 3 (3.1% vs 11.4%, P <0.001); hospital stay was significantly shorter (5.8±1.9 vs 7.5±1.7, P <0.001). There was no significant difference in overall survival and disease-free survival. CONCLUSIONS: MILR for HCC on MS is associated with equivalent perioperative and oncological outcomes to OLRs. Fewer major complications, posthepatectomy liver failures, ascites, and bile leaks can be obtained, with a shorter hospital stay. The combination of lower short-term severe morbidity and equivalent oncologic outcomes favor MILR for MS when feasible.

Model to predict major complications following liver resection for HCC in patients with metabolic syndrome.

BACKGROUND: Metabolic syndrome (MS) is rapidly growing as risk factor for HCC. Liver resection for HCC in patients with MS is associated with increased postoperative risks. There are no data on factors associated with postoperative complications. AIMS: The aim was to identify risk factors and develop and validate a model for postoperative major morbidity after liver resection for HCC in patients with MS, using a large multicentric Western cohort. MATERIALS AND METHODS: The univariable logistic regression analysis was applied to select predictive factors for 90 days major morbidity. The model was built on the multivariable regression and presented as a nomogram. Performance was evaluated by internal validation through the bootstrap method. The predictive discrimination was assessed through the concordance index. RESULTS: A total of 1087 patients were gathered from 24 centers between 2001 and 2021. Four hundred and eighty-four patients (45.2%) were obese. Most liver resections were performed using an open approach (59.1%), and 743 (68.3%) underwent minor hepatectomies. Three hundred and seventy-six patients (34.6%) developed postoperative complications, with 13.8% major morbidity and 2.9% mortality rates. Seven hundred and thirteen patients had complete data and were included in the prediction model. The model identified obesity, diabetes, ischemic heart disease, portal hypertension, open approach, major hepatectomy, and changes in the nontumoral parenchyma as risk factors for major morbidity. The model demonstrated an AUC of 72.8% (95% CI: 67.2%-78.2%) ( https://childb.shinyapps.io/NomogramMajorMorbidity90days/ ). CONCLUSIONS: Patients undergoing liver resection for HCC and MS are at high risk of postoperative major complications and death. Careful patient selection, considering baseline characteristics, liver function, and type of surgery, is key to achieving optimal outcomes.

Potential effects of virtual interventions for menopause management: a systematic review.

IMPORTANCE: Menopausal women are one of the fastest growing demographic groups globally. Virtual interventions have emerged as alternate avenues for menopausal women to manage and cope with their symptoms. OBJECTIVE: The purpose of this review is to summarize existing research on the potential effects of virtual interventions for menopause management. EVIDENCE REVIEW: This systematic review was written in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. MEDLINE, PsychINFO, CINAHL, AgeLine, ERIC, ProQuest, Nursing and Allied Health Database, PsychARTICLES, and Sociology Database were used for literature search and searched from conception to December 2021. Original studies, including randomized controlled trials and quasi-experimental studies, were included if they evaluated a virtual intervention for menopause management and investigated the effects of these interventions on physical and psychosocial outcomes and/or the feasibility of these interventions among menopausal women. Included studies were published in peer-reviewed journals and assessed for quality using the Critical Appraisal Skills Program Checklists. FINDINGS: A total of 16 articles were included in this review. Virtual interventions have the potential to improve physical health outcomes including body weight/body mass index/waist circumference, pain, blood pressure, and cholesterol. However, conflicting results were identified for the outcomes of vasomotor and endocrine symptoms, sleep, and sexual functioning. Virtual interventions might also improve psychosocial outcomes, including knowledge and patient-physician communication, although conflicting results were again identified for treatment decision-making ability, quality of life, and anxiety and depression. Virtual interventions were feasible in terms of being usable and cost-effective, and eliciting satisfaction and compliance among menopausal women. CONCLUSIONS AND RELEVANCE: Virtual interventions might have the potential to improve the physical and psychosocial health outcomes of menopausal women, although some conflicting findings arose. Future studies should focus on including diverse menopausal women and ethnic minorities, conducting research within low- to middle-income countries and communities, further exploring intervention design to incorporate features that are age and culture sensitive, and conducting full randomized controlled trials to evaluate the effects of the interventions.

Current clinical practice in patients with cardiac implantable electronic devices undergoing radiotherapy: a literature review.

Patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy (RT) are more common due to the ageing of the population. With newer CIEDs' implementing the complementary metal-oxide semiconductor (CMOS) technology which allows the miniaturization of CIED, it is also more susceptible to RT. Effects of RT on CIED ranges from device interference, device operational/memory errors of permanent damage. These malfunctions can cause life-threatening clinical effects. Cumulative dose is not the only component of RT that causes CIED malfunction, as neutron use and dose rate effect also affects CIEDs. The management of this patient cohort in clinical practice is inconsistent due to the lack of a consistent guideline from manufacturers and physician specialty societies. Our review will focus on the current clinical practice and the recently updated guidelines of managing patients with CIED undergoing RT. We aim to simplify the evidence and provide a simple and easy to use guide based on the recent guidelines.

Current Clinical Practice in Patients With Cardiac Implantable Electronic Devices (CIED) Undergoing Radiotherapy (RT).

Patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy (RT) becoming more common due to ageing of the population. With newer CIEDs implementing the complementary metal-oxide semiconductor (CMOS) technology which allows the miniaturisation of CIED, it is also more susceptible to RT. Effects of RT on CIED ranges from device interference, device operational/memory errors to permanent damage. These malfunctions can cause life threatening clinical effects. Cumulative dose is not the only component of RT that causes CIED malfunction, as neutron use and dose rate effect also affects CIEDs. The management of this patient cohort in clinical practice is inconsistent due to lack of a consistent guideline from manufacturers and physician specialty societies. Our review will focus on the current clinical practice and the recent updated guidelines of managing patients with CIED undergoing RT. We aim to simplify the evidence and provide a simple and easy to use guide based on the recent guidelines.

Atrial fibrillation detection using single lead portable electrocardiographic monitoring: a systematic review and meta-analysis.

OBJECTIVES: Recent technology advances have allowed for heart rhythm monitoring using single-lead ECG monitoring devices, which can be used for early diagnosis of atrial fibrillation (AF). We sought to investigate the AF detection rate using portable ECG devices compared with Holter monitoring. SETTING, PARTICIPANTS AND OUTCOME MEASURES: We searched the Medline, Embase and Scopus databases (conducted on 8 May 2017) using search terms related to AF screening and included studies with adults aged >18 years using portable ECG devices or Holter monitoring for AF detection. We excluded studies using implantable loop recorders and pacemakers. Using a random-effects model we calculated the overall AF detection rate. Meta-regression analysis was performed to explore potential sources for heterogeneity. Quality of reporting was assessed using the tool developed by Downs and Black. RESULTS: Portable ECG monitoring was used in 18 studies (n=117 436) and Holter monitoring was used in 36 studies (n=8498). The AF detection rate using portable ECG monitoring was 1.7% (95% CI 1.4 to 2.1), with significant heterogeneity between studies (p<0.001). There was a moderate linear relationship between total monitoring time and AF detection rate (r=0.65, p=0.003), and meta-regression identified total monitoring time (p=0.005) and body mass index (p=0.01) as potential contributors to heterogeneity. The detection rate (4.8%, 95% CI 3.6% to 6.0%) in eight studies (n=10 199), which performed multiple ECG recordings was comparable to that with 24 hours Holter (4.6%, 95% CI 3.5% to 5.7%). Intermittent recordings for 19 min total produced similar AF detection to 24 hours Holter monitoring. CONCLUSION: Portable ECG devices may offer an efficient screening option for AF compared with 24 hours Holter monitoring. PROSPERO REGISTRATION NUMBER: CRD42017061021.

Domino Insertion-Coupling Synthesis of Solid-State Luminescent Propynylidene Indolones.

The compound class of 3-arylpropynylidene indolones, key intermediates in consecutive three-component syntheses of various indole-based chromophores with peculiar emission characteristics, are readily synthesized by a domino insertion-coupling synthesis with an electronically diverse substitution pattern in moderate to excellent yields. The title compounds are formed in E/Z-ratios from 100:0 to 0:100. Besides structure elucidation by NMR-spectroscopy and X-ray structure analysis, DFT calculations have been employed to rationalize the observed stereoselectivity. The photophysical properties of 3-arylpropynylidene indolones are characterized by intense, tunable, solid-state emission of N-substituted derivatives as quantified for drop-cast films. The electronic ground state structure was corroborated by DFT and TD-DFT calculations, showing that gradient-corrected exchange and correlation PBE (Perdew-Burke-Ernzerhof) functionals can be successfully employed to correctly reproduce the observed absorption characteristics of merocyanine derivatives. The huge Stokes shifts strongly depend on the electronic substitution pattern as supported by Hammett-Taft correlations.

Toward metal complexes that can directionally walk along tracks: controlled stepping of a molecular biped with a palladium(II) foot.

We report on the design, synthesis, and operation of a bimetallic molecular biped on a three-foothold track. The "walker" features a palladium(II) complex "foot" that can be selectively stepped between 4-dimethylaminopyridine and pyridine ligand sites on the track via reversible protonation while the walker remains attached to the track throughout by means of a kinetically inert platinum(II) complex foot. The substitution pattern of the three ligand binding sites, together with the kinetic stability of the metal-ligand coordination bonds, affords the two positional isomers a high degree of metastability, meaning that altering the chemical state of the track does not automatically instigate stepping in the absence of an additional stimulus (heat in the presence of a coordinating solvent). The use of metastable metal complexes for foot-track interactions offers a promising alternative to dynamic covalent chemistry for the design of small-molecule synthetic molecular walkers.

Sequence-specific peptide synthesis by an artificial small-molecule machine.

The ribosome builds proteins by joining together amino acids in an order determined by messenger RNA. Here, we report on the design, synthesis, and operation of an artificial small-molecule machine that travels along a molecular strand, picking up amino acids that block its path, to synthesize a peptide in a sequence-specific manner. The chemical structure is based on a rotaxane, a molecular ring threaded onto a molecular axle. The ring carries a thiolate group that iteratively removes amino acids in order from the strand and transfers them to a peptide-elongation site through native chemical ligation. The synthesis is demonstrated with ~10(18) molecular machines acting in parallel; this process generates milligram quantities of a peptide with a single sequence confirmed by tandem mass spectrometry.

A scalable synthesis of 5,5'-dibromo-2,2'-bipyridine and its stepwise functionalization via Stille couplings.

The synthesis of 5,5'-dibromo-2,2'-bipyridine and 5-bromo-2,2'-bipyridine, useful intermediates for elaboration into more complex ligands through metal-catalyzed coupling reactions, can be efficiently conducted on a multigram scale from inexpensive starting materials. The described procedure is reliably scalable and suitable for the synthesis of tens of grams of 5,5'-dibromo-2,2'-bipyridine. 5-Bromo-2,2'-bipyridine is produced as a minor product. The 5,5'-disubstituted-2,2'-bipyridine motif has excellent coordination properties and is a versatile building block for the synthesis of functional materials (including biodiagnostics, photovoltaics and organic light-emitting diodes) and complex molecular topologies (including catenanes and trefoil and pentafoil knots). The selective stepwise functionalization of 5,5'-dibromo-2,2'-bipyridine by consecutive Stille couplings is therefore illustrated and documented in detail. The synthesis of 5,5'-dibromo-2,2'-bipyridine takes 4-5 d: 1 d to prepare the key intermediate 2,2'-bipyridine dihydrobromide, 3 d for its reaction with bromine in a steel bomb reaction vessel and 8 h to isolate and purify the final product.

Phosphorus-based functional groups as hydrogen bonding templates for rotaxane formation.

We report on the use of the hydrogen bond acceptor properties of some phosphorus-containing functional groups for the assembly of a series of [2]rotaxanes. Phosphinamides, and the homologous thio- and selenophosphinamides, act as hydrogen bond acceptors that, in conjunction with an appropriately positioned amide group on the thread, direct the assembly of amide-based macrocycles around the axle to form rotaxanes in up to 60% yields. Employing solely phosphorus-based functional groups as the hydrogen bond accepting groups on the thread, a bis(phosphinamide) template and a phosphine oxide-phosphinamide template afforded the corresponding rotaxanes in 18 and 15% yields, respectively. X-ray crystallography of the rotaxanes shows the presence of up to four intercomponent hydrogen bonds between the amide groups of the macrocycle and various hydrogen bond accepting groups on the thread, including rare examples of amide-to-phosphinamide, -thiophosphinamide, and -selenophosphinamide groups. With a phosphine oxide-phosphinamide thread, the solid-state structure of the rotaxane is remarkable, featuring no direct intercomponent hydrogen bonds but rather a hydrogen bond network involving water molecules that bridge the H-bonding groups of the macrocycle and thread through bifurcated hydrogen bonds. The incorporation of phosphorus-based functional groups into rotaxanes may prove useful for the development of molecular shuttles in which the macrocycle can be used to hinder or expose binding ligating sites for metal-based catalysts.

Unusual solid-state luminescent push-pull indolones: a general one-pot three-component approach.

In a consecutive three-component cyclocarbopalladation, Sonogashira coupling, Michael addition sequence 4-aminopropenylidene indolones, i.e., terminally fixed push-pull chromophores, are obtained in yields as high as 99%. Most remarkable, however, is the pronounced orange red solid state fluorescence displaying large Stokes shifts of these merocyanines, in particular, since all chromophores are nonfluorescent in solution.

Nitrone [2]rotaxanes: simultaneous chemical protection and electrochemical activation of a functional group.

We report on the use of the hydrogen-bond-accepting properties of neutral nitrone moieties to prepare benzylic amide macrocycle-containing [2]rotaxanes in yields as high as 70%. X-ray crystallography showed the presence of up to four intercomponent hydrogen bonds between the amide groups of the macrocycle and the two nitrone groups of the thread. Dynamic (1)H NMR studies of the rates of macrocycle pirouetting in nonpolar solutions indicated that the amide-nitrone hydrogen bonds are particularly strong (approximately 1.3 and approximately 0.2 kcal mol(-1) stronger than similar amide-ester and amide-amide interactions, respectively). In addition to polarizing the N-O bond through hydrogen bonding, the rotaxane structure affects the chemistry of the nitrone groups in two significant ways: first, the intercomponent hydrogen bonding activates the nitrone groups to electrochemical reduction, a one-electron-reduction of the rotaxane being stabilized by a remarkable 400 mV (8.1 kcal mol(-1)) with respect to the same process in the thread; second, however, encapsulation protects the same functional groups from chemical reduction with an external reagent (and slows electron transfer to and from the electroactive groups in cyclic voltammetry experiments). Mechanical interlocking with a hydrogen-bonding molecular sheath thus provides a route to an encapsulated polarized functional group and radical anions of significant kinetic and thermodynamic stability.

Catalytic alkynone generation by Sonogashira reaction and its application in three-component pyrimidine synthesis.

The Sonogashira alkynylation of acid chlorides can be efficiently conducted in less than an hour by performing the reaction in tetrahydrofuran as a solvent and in the presence of one stoichiometrically necessary equivalent of triethylamine as a base. This approach also opens new avenues for consecutive one-pot multicomponent reactions. As an example, the one-pot three-component pyrimidine synthesis illustrates the versatility of this modified Sonogashira protocol as an entry to diversity-oriented heterocycle synthesis in a one-pot fashion. The protocol can be completed within a few hours.