Development of an indicator for the direct visualization of radical intermediates in organic reactions

Abstract

A color-indicator based on a derivative of rhodamine amide was developed for the detection of radical intermediates in organic reactions. This derivative showed sensitive color changes for various radical intermediates initiated by chemical reagents or UV light.

The Photoinduced Metal‐Free Hydrotrifluoromethylation of Vinyl Phosphonates or Phosphine Oxides

“…of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) was added, and the reaction was completely inhibited (Equation 2). Also, when a radical indicator was added, a pink solution was observed as well (see ESI). These results suggest that a radical mechanism was involved (Scheme ).…”

“…Acetone can absorb electrons with the highest yield after 12 h in all solvents tested (61 %, Table 1, entries 1-11). The reaction time could be reduced to 6 h after which no 1a was detected ( Table 1, entries [12][13][14]. Argon was effective in this reaction as it gave a higher yield compared to the reaction performed in air ( Table 1, entry 15; oxygen in the air quenches radical intermediates).…”

Study of Rhodamine‐Based Fluorescent Probes for Organic Radical Intermediates

“…A series of rhodamine-based fluorescent probes was synthesized via the reaction of rhodamine B with substituted benzylamines (1)(2)(3)(4)(5), alkyl amines (6-10), or aryl amines (11-22, Scheme 2). These compounds were then used in the detection of organic radical intermediates (Scheme 3), produced from the thermal homolysis of traditional radical initiators such as di-tbutyl peroxide (DTBP), 2,2-azobisisobutyronitrile (AIBN), t-butyl peroxyacetate (TBPA), and t-butyl hydroperoxide (TBHP).…”

“…However, the in situ visualization of radical intermediates for organic reactions is challenging. In 2017, we reported a sensitive color‐indicator for the detection of radical intermediates in organic reactions [5] . This indicator is suitable to detect radicals in colorless or light‐colored solution in specific solvents [6] .…”

“…In 2017, we reported a sensitive color-indicator for the detection of radical intermediates in organic reactions. [5] This indicator is suitable to detect radicals in colorless or lightcolored solution in specific solvents. [6] For reactions whose color are deep, it is difficult to distinguish color changes; thus, the indicator cannot be used in these situations.…”