p-Hydroxyphenacyl photoremovable protecting groups - Robust photochemistry despite substituent diversity.
A broadly based investigation of the effects of a diverse array of substituents on the photochemical rearrangement ofp-hydroxyphenacyl esters has demonstrated that common substituents such as F, MeO, CN, CO2R, CONH2, and CH3have little effect on the rate and quantum efficiencies for the photo-Favorskii rearrangement and the release of the acid leaving group or on the lifetimes of the reactive triplet state. A decrease in the quantum yields across all substituents was observed for the release and rearrangement when the photolyses were carried out in buffered aqueous media at pHs that exceeded the ground-state pKaof the chromophore where the conjugate base is the predominant form. Otherwise, substituents have only a very modest effect on the photoreaction of these robust chromophores.
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Richard S
RS
Givens
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Kenneth
K
Stensrud
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Peter G
PG
Conrad
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Abraham L
AL
Yousef
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Chamani
C
Perera
Department of Chemistry, University of Kansas Lawrence, Lawrence, KS 66045, USA.
Sanjeewa N
SN
Senadheera
Research Centre for Toxic Compounds in the Environment (RECETOX) and Department of Chemistry, Faculty of Science, Masaryk University, Kamenice3, 625 00 Brno, Czech Republic.
Dominik
D
Heger
Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
Jakob
J
Wirz
pH; pKa; photorelease; solvent effects; substituent