Stille coupling quinoxalines

Dipyrrolylquinoxalines with extended ehromophores are efficient fluorimetric sensors for pyrophosphate. The Stille coupling of 5,8-dibromo-2,3-di(pyrrol-2-yl) quinoxaline with aryItributylstannane produced 5,8-diaryl substituted quinoxalines 205 as possible sensors [100]. 

The Pd-mediated cross-coupling reactions on the pyrazine ring of quinoxaline with organometallic reagents are more cumbersome. In one example, the Stille reaction between 2-chloroquinoxaline 87 and benzylstannane 88, attainable from the SN2 displacement of... 

A very elegant experiment has been done by van der Waals and his group recently (30) in which the phosphorescence modulation due to coherent coupling of the triplet spin levels with a strong microwave field of resonance frequencies was demonstrated. The system was quinoxaline-d in durene, and the zf transition at 1.001 GHz was coupled to the microwave field. The experiment was done in the following manner. The excitation was cut off after the steady state was accomplished. A few seconds later, the radiative level was empty, yet the other level was still densely populated. At this instant, powerful microwave pulses of 1.001 GHz frequency but of different pulse widths were applied in different experiments. The population of the radiative level, and thus the intensity of pulse of the phosphorescence produced, is shown to be a periodic function... 

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