New fluorogenic probes for oxygen and carbene transfer: A sensitive assay for single bead-supported catalysts

A high-throughput screening assay for atom transfer catalysis has been deve loped. This assay is based on two probes, developed herein, which generate highly fluorescent products upon carbene or oxygen atom transfer. The emiss ion wavelength of probes 1 and 5 shift significantly (up to 90 nm) upon epo xidation, allowing detection of product at 3% conversion. Probe 7 is not fl uorescent, while fluorescence emission by carbene insertion/rearrangement p roduct 8 allows detection at less than 1% conversion. Such sensitivity allo ws for examination of single-bead reactions in a high throughput array form at (1536 wells per plate), and provides a broad detection window ranging fr om single to high turnover numbers. Thousands of metal complexes are evalua ted in a single screening experiment. Preliminary screening of a diverse li gand library with probe 7 in the presence of Rh(II) uncovered new catalysts capable of cyclopropanation and C-H insertion.