Highly Strained C-C Bonds: 3-(1'-Hydroxy-4'-isopropyl-2',2'-dimethyl-1',2'-dihydrobenzocyclobuten-1'-yl)-3-methyl-2-butanone Ethylene Acetal, (I), and (3S^*,1'S^*)-3-Acetoxy-2-(1'-hydroxy-1',2'-dihydrobenzocyclobuten-1'-yl)-2-methylpentane, (II)

The crystal structures of the title compounds, C₂₀H₃₀O₃ (I) and C₁₆H₂₂O₃ (II), are described. The benzocyclobutene rings in (I) and (II) are approximately planar. The lengths of the Csp³-Csp³ bonds in the cyclobutene rings of (I) and (II) are 1.659 (2) and 1.596 (2) Å, respectively. The C-C bond elongation observed in (I) may be ascribed to steric congestion and/or electronic effects on the bond exerted by the methyl groups and the alkyl side chain attached to the cyclobutenol moiety, together with a ring strain expected for a four-membered ring system.

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