Mechanistic Studies of Ethylene Hydrophenylation Catalyzed by Bipyridyl Pt(II) Complexes

This article discusses mechanistic studies of ethylene hydrophenylation catalyzed by bipyridyl Pt(II) complexes

Counteranion and Solvent Assistance in Ruthenium-Mediated Alkyne to Vinylidene Isomerizations

The complex [Cp*RuCl(iPr2PNHPy)] (1) reacts with 1-alkynes HC≡CR (R = COOMe, C6H4CF3) in dichloromethane furnishing the corresponding vinylidene complexes [Cp*Ru≡C≡CHR(iPr2PNHPy)]Cl (R = COOMe (2a- Cl), C6H4CF3 (2b-Cl)), whereas reaction of 1 with NaBPh4 in MeOH followed by addition of HC≡CR (R = COOMe, C6H4CF3) yields the metastable π-alkyne complexes [Cp*Ru(η2-HC≡CR)(iPr2PNHPy)][BPh4] (R = COOMe (3a-BPh4), C6H4CF3 (3b-BPh4)). The transformation of 3a-BPh4/3b-BPh4 into their respective vinylidene isomers in dichloromethane is very slow and requires hours to its completion. However, this process is accelerated by addition of LiCl in methanol solution. Reaction of 1 with HC≡CR (R = COOMe, C6H4CF3) in MeOH goes through the intermediacy of the π-alkyne complexes [Cp*Ru(η2-HC≡CR)(iPr2PNHPy)]Cl (R = COOMe (3a-Cl), C6H4CF3 (3b-Cl)), which rearrange to vinylidenes in minutes, i.e., much faster than their counterparts containing the [BPh4]− anion. The kinetics of these isomerizations has been studied in solution by NMR. With the help of DFT studies, these observations have been interpreted in terms of chloride- and methanolassisted hydrogen migrations. Calculations suggest participation of a hydrido−alkynyl intermediate in the process, in which the hydrogen atom can be transferred from the metal to the β-carbon by means of species with weak basic character acting as proton shuttles

Catalytic Transformations of Alkynes via Ruthenium Vinylidene and Allenylidene Intermediates

NOTICE: This is the peer reviewed version of the following book chapter: Varela J. A., González-Rodríguez C., Saá C. (2014). Catalytic Transformations of Alkynes via Ruthenium Vinylidene and Allenylidene Intermediates. In: Dixneuf P., Bruneau C. (eds) Ruthenium in Catalysis. Topics in Organometallic Chemistry, vol 48, pp. 237-287. Springer, Cham. [doi: 10.1007/3418_2014_81]. This article may be used for non-commercial purposes in accordance with Springer Verlag Terms and Conditions for self-archiving.Vinylidenes are high-energy tautomers of terminal alkynes and they can be stabilized by coordination with transition metals. The resulting metal-vinylidene species have interesting chemical properties that make their reactivity different to that of the free and metal π-coordinated alkynes: the carbon α to the metal is electrophilic whereas the β carbon is nucleophilic. Ruthenium is one of the most commonly used transition metals to stabilize vinylidenes and the resulting species can undergo a range of useful transformations. The most remarkable transformations are the regioselective anti-Markovnikov addition of different nucleophiles to catalytic ruthenium vinylidenes and the participation of the π system of catalytic ruthenium vinylidenes in pericyclic reactions. Ruthenium vinylidenes have also been employed as precatalysts in ring closing metathesis (RCM) or ring opening metathesis polymerization (ROMP). Allenylidenes could be considered as divalent radicals derived from allenes. In a similar way to vinylidenes, allenylidenes can be stabilized by coordination with transition metals and again ruthenium is one of the most widely used metals. Metalallenylidene complexes can be easily obtained from terminal propargylic alcohols by dehydration of the initially formed metal-hydroxyvinylidenes, in which the reactivity of these metal complexes is based on the electrophilic nature of Cα and Cγ, while Cβ is nucleophilic. Catalytic processes based on nucleophilic additions and pericyclic reactions involving the π system of ruthenium allenylidenes afford interesting new structures with high selectivity and atom economy

James Vastine oral history interview by Yael V. Greenberg, August 5, 2003

James Vastine relates his experience as part of the University of South Florida 1960 charter class. Mr. Vastine discusses the campus, classes and faculty as it was in the early years of the University. Additionally Mr. Vastine speaks about the development, growth and nature of the USF Library, and his 30+ years as a librarian at this institution

An outbreak of epidemic keratoconjunctivitis in a regional ophthalmology clinic in New South Wales

The objective of the study was to identify the extent and cause of an outbreak of epidemic keratoconjunctivitis (EKC). The study design was active case finding and a case-control study of clinic patients who developed symptoms of EKC between 31 December 2005 and 31 March 2006. The main outcome measures were clinical procedures carried out and clinicians seen during clinic visit. Significantly more cases than controls had tonometry with instillation of anaesthetic drops (OR 16·5, 95% CI 3·9–145·1, P<0·01), optical coherence tomography (OR 4·7, 95% CI 1·2–21·9, P=0·01), or instillation of dilating drops by an orthoptist (OR 2·3, 95% CI 1·1–4·7, P=0·01). Significantly more cases than controls were seen by one orthoptist (OR 21·8, 95% CI 8·2–60·0, P<0·01). Transmission of EKC within the clinic was probably due to contamination of either or both the anaesthetic drops and the tonometer head in the room used by an orthoptist. A comprehensive suite of strategies is required to prevent healthcare-associated EKC

Impact of panniculectomy on transplant candidacy of obese patients with chronic kidney disease declined for kidney transplantation because of a high-risk abdominal panniculus: A pilot study

BackgroundObese patients can develop a large lower abdominal panniculus (worsened by significant weight loss). Patients with advanced chronic kidney disease (CKD) affected by this obesity-related sequela are not infrequently declined for kidney transplantation because of the high risk for serious wound-healing complications. We hypothesized that pretransplant panniculectomy in these patients would (1) render them transplant candidates, and (2) result in low posttransplant wound-complication rates.MethodsIn a pilot study, adult patients with CKD who had a high-risk panniculus as the only absolute contraindication to kidney transplantation subsequently were referred to a plastic surgeon to undergo a panniculectomy in order to become transplant candidates. We analyzed the effect of panniculectomy on (1) transplant candidacy and (2) wait list and transplant outcomes (04/2008-06/2014).ResultsOverall, 36 patients had panniculectomy (median prior weight loss, 38&nbsp;kg); all were wait-listed with these outcomes: (1) 22 (62%) patients were transplanted; (2) 7 (19%) remain listed; and (3) 7 (19%) were removed from the wait list. Survival after panniculectomy was greater for those transplanted versus not transplanted (at 5&nbsp;years, 95% vs 35%, respectively; P&nbsp;=&nbsp;.002). For the 22 kidney recipients, posttransplant wound-complication rate was 5% (1 minor subcutaneous hematoma).ConclusionFor obese CKD patients with a high-risk abdominal panniculus, panniculectomy was highly effective in obtaining access to the transplant wait list and successful kidney transplantation. This approach is particularly pertinent for CKD patients because they are disproportionally affected by the obesity epidemic and because obese CKD patients already face multiple other barriers to transplantation