Two germaoxetanes from a germene: Formation and structure

Article abstract of DOI:10.1021/om00052a024

Dimesitylfluorenylidenegermane (1) reacts very readily with aldehydes and ketones, according to a [2 + 2] cycloaddition, leading to the corresponding germaoxetanes. These four-membered-ring heterocycles are quite stable, mainly due to the large steric hindrance of the substituents. In the case of acetone, reaction with the enolic form has been observed, followed by a germanotropic rearrangement. Germaoxetanes 3 (monoclinic, P2₁/n, a = 12.668 (5) ?, b = 16.794 (6) ?, c = 14.600 (5) ?, β = 90.25 (3)°, V = 3106 (2) ?³, Z = 4, R = 0.0525) and 4 (monoclinic, P2₁/c, a = 22.807 (5) ?, b = 17.713 (6) ?, c = 18.425 (4) ?, β = 102.64 (2)°, V = 7263 (3) ?³, Z = 8, R = 0.0697), obtained from benzaldehyde and benzophenpne, have been characterized by X-ray diffraction methods and their data compared to those of the acyclic digermoxane 6 (triclinic, P1, a = 13.002 (3), ?, b = 14.962 (2) ?, c = 16.094 (1) ?, α = 98.92 (1)°, β = 95.90 (2)°, γ = 114.52 (1)°, V = 2765 (1) Aγ³, Z = 2, R = 0.0781) prepared by hydrolysis of germene 1.