Methylene blue, astatination

Methylenation using diazomethane, 2 78 Methylene, 29 303-304 Methylene blue, astatination, 31 77 Methylenephosphoranes, reaction with hexafluoroacetone, 30 258... 

Astatination of the diazonium salt of 4-amino-methylene blue led to only 10% yield of 4-astato-methylene blue (VI). Alternatively, 4-astato-methylene blue was rapidly synthesized by heterogeneous nucleophilic isotopic exchange in the presence of 18-crown-6 ether at 80° C, with 4-iodo-methylene blue. The product was separated and identified by TLC yields ranged from 50 to 65% 41). Additionally, 2-astato-8-iodo-methylene blue (VII) has similarly been prepared in 60% yield from 2,8-diiodo-methylene blue 41). 

Attempts at electrophilic astatination of methylene blue with At/chloramine-T have proved ineffective 41). 

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