Thieme Chemistry Journals Awardees - Where Are They Now? A Cascade Synthesis of 1,2,4-Triazin-3(2H)-ones Using Nitrogen-Substituted Isocyanates

A cascade synthesis of 1,2,4-triazin-3(2H)-ones is reported from readily accessible alpha-amino ketones and phenyl carbazate as a masked N-isocyanate precursor. The mild protocol provides a simple route to products with substitution patterns which are difficult to form directly. This also presents the first N-isocyanate cascade requiring the use of acidic conditions, which accelerates formation of the hydrazone intermediate and the cyclization step. This cascade further highlights that high control can be achieved in reactions forming highly reactive N-isocyanate intermediates.