Caryophyllene rearrangement products. Part I. The crystal structure and absolute stereochemistry of caryophyllene ‘iodonitrosite’, a stable nitroxide radical

Abstract

The crystal structure and absolute stereochemistry of caryophyllene ‘iodonitrosite’, a stable nitroxide radical, have been established using three-dimensional X-ray diffractometer data. The crystals are orthorhombic, space group P2₁2₁2₁, with four molecules of C₁₅H₂₄IN₂O₃ in a unit cell of dimensions a 6·78, b8·24, c 30·49 Å. The structure has been refined by least-squares methods to a final residual (R) of 0·069, over 1041 independent reflexions. Caryophyllene iodonitrosite is tricyclic with a four-membered ring trans-fused to a seven-membered ring, which is in turn cis-cridged to a six-membered ring. The nitroxide bond length is 1·308 ± 0·022 Å, and corresponds to a three-electron bond. This analysis also confirms the absolute stereochemistry assigned to caryophyllene.