Rac-2′,3a,6,6,6′,6′-Hexamethyl-3a,3b,6,7-tetra-hydrospiro-[benzo[2,3]cyclopropa[1,2-c]pyrazole-1,1′-cyclo-hepta[2,4]diene]

• Main Authors: Marcus Baumann, Sophie Lapraille, Ian R. Baxendale
• Format: Article
• Language: English
• Published: MDPI AG 2017-08-01
• Series: Molbank
• Subjects: eucarvone; dimerization; cycloaddition; tosylhydrazone; 1,3-dipole; molecular rearrangement; Bamford-Stevens reaction
• Online Access: https://www.mdpi.com/1422-8599/2017/3/M948
• ISSN: 1422-8599

This note describes a novel reaction cascade in which a tosylhydrazone derivative of eucarvone undergoes a non-classical dimerization process under basic conditions. The key step in this sequence is a dipolar cycloaddition between a diazo species and a transient cyclopropene. A proposed mechanism for this sequence is presented that is supported by single crystal X-ray analysis of the resulting dimer. We believe this unique transformation is of note as it highlights a neat and efficient entry to complex polycyclic architectures containing an embedded pyrazoline moiety.