Synthesis and X-Ray Crystal Structure Analysis of 1,4-Epoxy-4-methyl-1H,4H-2,3-benzodioxepin

Ozonolysis of 2-methyl-1H-indene (1) afforded the stable secondary ozonide 1,4-epoxy-4-methyl-1H,4H-2,3-benzodioxepin (2). This compound crystallizes in two polymorphic forms, depending on the solvent used. The monoclinic form 2a containing two symmetry-independent molecules (enantiomers) is obtained by crystallization from dichloromethane. In contrast, the orthorhombic modification 2b is obtained from ethyl acetate solution and crystallizes as a conglomerate of enantiomerically pure single crystals. Additionally, the ring-opened product 2-(2-oxopropyl)benzoic acid (3) was obtained and investigated by X-ray crystal structure analysis.