No abstract

Intramolecularly hydrogen bonded o-hydroxybenzaldehyde (OHBA-C) isblated in 12 K rare gas matrices photolyzes to a non-hydrogen-bonded rotamer (OHBA-F). IR spectra of OHBA-C, OHBA-F, and several model and isotopically substituted compounds are consistent with identification of the OHBA-F conformer as that formed by 180-deg rotation of both the hydroxy and aldehyde groups. For the two rotamers, electronic absorption, excitation, and emission spectra are presented together with time-resolved emission measurements and estimates of a ground-state reaction enthalpy. From these data, it is proposed that the S, state of OHBA-C is an n,r* hydrogen atom transfer state, and Sz is a r,r* proton-transfer state with a large (-18 kcal) barrier to reaction. Rotamerization is reversed by SI or S2 excitation of OHBA-F. The conversion of OHBA-C to OHBA-F is -5 times as efficient as the reverse process upon excitation at the respective SI 0-0 energies. An increase in photolysis quantum yield of OHBA-C is measured at energies well above the 0-0 energy and may correspond to reaction over the proposed -8 kcal SI barrier.

No abstract

No abstract

A new tetrafluorophenol activated resin that facilitates the use of 19F NMR to quantitate loading is presented. This new resin provides a useful tool for acylation, and a novel activated polymeric sulfonate ester to generate sulfonamides. This activated resin reacts with a wide scope of N-nucleophiles including primary and secondary amines, and anilines. This new activated resin methodology provides a powerful tool for pure single-compound library synthesis.