Control of Conformation and Reactivity in Pentafluorosulfanyl and Tetrafluorosulfanyl Substituted Aliphatic Compounds

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In this project funded by the Chemical Synthesis program of the Chemistry Division, Professor John Welch of the University at Albany is developing new fluorine containing functional groups. Fluorinated compounds are widely employed in life sciences and materials research. Nearly 20% of all pharmaceuticals and 40% of all agrochemicals contain fluorine. Fluorination and fluorinated functional groups have added value and utility to materials for 75 years yet it has been increasingly apparent that these useful substituents can be accompanied by undesirable environmental effects. Prof. Welch is training graduate students to handle extraordinarily reactive reagents to prepare novel fluorinated reactants. Prof. Welch operates and makes available to the scientific community a dedicated laboratory equipped with the necessary infrastructure for the preparation, purification and characterization of both liquid and gaseous reactive fluorinated intermediates and synthons. The relationship between structure and reactivity of aliphatic fluorinated hypervalent sulfur compounds is under investigation. Although the chemistry of the pentafluorosulfanyl group is very much in its infancy, the Welch group is exploring the use of environmentally more benign hypervalent fluorinated sulfur compounds to deliver the desired effects of fluorination while mitigating the undesirable aspects, e.g., by decomposing in an environmentally benign manner. The influence of steric demand, electronegativity and dipole moment on the physical properties, conformation, and selectivity of beta-lactams, amino acids and peptides containing fluorinated hypervalent sulfur is being explored. The role of trifluoromethyl substitution in the SF5-group (i.e. the new SF4(CF3) group) is under investigation. In comparing the SF5 and SF4(CF3) substituents, differences in selectivity and reactivity will be examined. An effort will be made to establish whether such differences correlate with trends in dipole moment or electron-withdrawing ability of these two new, heavily fluorinated substituents.