Functionality-Matched Semicarbazone Reagents Allow Access to X-ray Quality Crystals and Solids of Diverse Organic Molecules

A flexible approach to crystalline compounds was developed: lipophilic structures of interest were connected to pro-crystalline semicarbazone reagents via copper-catalyzed azide-alkyne cycloaddition or Brønsted-Lowry acid-base reactions. A variety of lipophilic structures, including esters, carbamates, acids and amines were converted into crystalline solids as determined by powder X-ray diffraction (mp 134 to >240 °C). Single crystal X-ray diffraction revealed hydrogen-bond interactions between the semicarbazone and charged ammonium or acetate groups that may aid in ordering the crystals.