Spectacular Differences in the Thermal Behavior and the Aromatic Substitution Reactions of 5-Diazouracil and 5-Diazo-3-methyluracil

Article abstract of DOI:10.1021/jo00297a007

5-Diazo-3-methyluracil reacts with varied benzenes to yield 3-methyl-5-aryluracils by apparent singlet carbene addition and homolytic rearrangement of spironorcaradiene intermediates. 5-Diazouracil, however, thermolyzes with rearrangement and loss of nitrogen to form (2,5-dioxo-3-imidazolin-4-yl)methylene, which reacts with benzene and cyclooctane to give 5-cycloheptatrienylidene-2,4-imidazolidinedione and (E)- and (Z)-5-(cyclooctylmethylene)-2,4-imidazolidinediones, respectively.