67 research outputs found
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
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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
Coordinatively Unsaturated T-Shaped Platinum(II) Complexes Stabilized by Small N-Heterocyclic Carbene Ligands. Synthesis and Cyclometalation
Benzene C−H Bond Activation in Carboxylic Acids Catalyzed by O-Donor Iridium(III) Complexes: An Experimental and Density Functional Study
Transition-State Charge Transfer Reveals Electrophilic, Ambiphilic, and Nucleophilic Carbon−Hydrogen Bond Activation
Reactivity of Coordinatively Unsaturated Bis(N-heterocyclic carbene) Pt(II) Complexes toward H 2
Policies and clinical practices relating to the management of gestational diabetes mellitus in the public health sector, South Africa – a qualitative study
BACKGROUND: Women with a prior gestational diabetes have an increased lifetime risk of developing type 2
diabetes. Although post-partum follow-up for GDM women is essential to prevent progression to type 2 diabetes, it
is poorly attended. The need for health systems interventions to support postpartum follow-up for GDM women is
evident, but there is little knowledge of actual current practice. The aim of this study was to explore current policies
and clinical practices relating to antenatal and post-natal care for women with GDM in South Africa, as well as
health sector stakeholders’ perspectives on the barriers to – and opportunities for – delivering an integrated
mother - baby health service that extends beyond the first week post-partum, to the infant’s first year of life.
METHODS: Following a document review of policy and clinical practice guidelines, in-depth interviews were
conducted with 11 key informants who were key policy makers, health service managers and clinicians working in
the public health services in South Africa’s two major cities (Johannesburg and Cape Town). Data were analysed
using qualitative content analysis procedures.
RESULTS: The document review and interviews established that it is policy that health services adhere to
international guidelines for GDM diagnosis and management, in addition to locally developed guidelines and
protocols for clinical practice. All key informants confirmed that lack of postpartum follow-up for GDM women is a
significant problem. Health systems barriers include fragmentation of care and the absence of standardised
postnatal care for post-GDM women. Key informants also raised patient - related challenges including lack of
perceived future risk of developing type 2 diabetes and non-attendance for postpartum follow up, as barriers to
postnatal care for GDM women. All participants supported integrated primary health services but cautioned against
overloading health workers.
CONCLUSION: Although there is alignment between international guidelines, local policy and reported clinical
practice in the management of GDM, there is a gap in continuation of care in the postpartum period. Health
systems interventions that support and facilitate active follow-up for women with prior GDM are needed if high
rates of progression to type 2 diabetes are to be avoided
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