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Mild silver-mediated geminal difluorination of styrenes using an air- and moisture-stable fluoroiodane reagent.

ABSTRACT: An air- and moisture-stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the C?F bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium-isotope-labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.

SUBMITTER: Ilchenko NO

PROVIDER: S-EPMC4501311 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Mild silver-mediated geminal difluorination of styrenes using an air- and moisture-stable fluoroiodane reagent.

Ilchenko Nadia O NO Tasch Boris O A BO Szabó Kálmán J KJ

Angewandte Chemie (International ed. in English) 20141021 47

An air- and moisture-stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the CF bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium-isotope-labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate. ...[more]

PMID: 25335468

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Project description:BACKGROUND AND AIMS:Annually resolved biological climate proxies beyond the altitudinal and latitudinal distribution limit of trees are rare. In such regions, several studies have demonstrated that annual growth rings of dwarf shrubs are suitable proxies for palaeoclimatic investigations. In High Asia, the pioneer work of Liang et al. (Liang E, Lu X, Ren P, Li X, Zhu L, Eckstein D, 2012. Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy. Annals of Botany109: 721-728) confirmed the suitability of shrub growth-ring chronologies for palaeoclimatic research. This study presents the first sensitivity study of an annually resolved ?18O time series inferred from Wilson juniper (Juniperus pingii var. wilsonii) from the northern shoreline of lake Nam Co (Tibetan Plateau). METHODS:Based on five individual dwarf shrub discs, a statistically reliable ?18O chronology covering the period 1957-2009 was achieved (expressed population signal = 0.80). Spearman's correlation analysis between the ?18O chronology and climate variables from different sources was applied. In a first step, the suitability of various climate data was evaluated. KEY RESULTS:Examinations of climate-proxy relationships revealed significant negative correlations between the ?18O shrub chronology and summer season moisture variability of the previous and current year. In particular, relative humidity of the previous and current vegetation period significantly determined the proxy variability (? = -0.48, P < 0.01). Furthermore, the ?18O variability of the developed shrub chronology significantly coincided with a nearby tree-ring ?18O chronology of the same genus (r = 0.62, P < 0.01). CONCLUSIONS:The ?18O shrub chronology reliably recorded humidity variations in the Nam Co region. The chronology was significantly correlated with a nearby moisture-sensitive tree-ring ?18O chronology, indicating a common climate signal in the two chronologies. This climate signal was likely determined by moisture variations of the Asian summer monsoon. Local climate effects were superimposed on the supra-regional climate signature of the monsoon circulation. Opposing ?18O values between the two chronologies were interpreted as plant-physiological differences during isotopic fractionation processes.

Dataset Information

Mild silver-mediated geminal difluorination of styrenes using an air- and moisture-stable fluoroiodane reagent.

Publications

Mild silver-mediated geminal difluorination of styrenes using an air- and moisture-stable fluoroiodane reagent.

Similar Datasets

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