147752-98-5Relevant academic research and scientific papers
Unsaturated germanium and phosphorus compounds: Reactions of germaphosphenes with α-ethylene aldehydes and ketones
Ranaivonjatovo,Escudié,Couret,Declercq,Dubourg,Satgé
, p. 1674 - 1681 (2008/10/08)
GermaphosphenesMes2Ge=PR (R: 2,4,6-triisopropylphenyl (Is), 1;2,4,6-tri-tert-butylphenyl (Ar), 2) react with α-ethylene aldehydes and ketones to give [2 + 2] and [2 + 4] cycloadditions (for aldehydes) and [2 + 4] cycloadditions and 1,2-additions (for ketones). Four- and six-membered ring derivatives can be easily differentiated by 31P NMR chemical shifts which are, respectively, +36 to +89 ppm and -33 to -77 ppm. 5a′, obtained from 2 and crotonaldehyde, has been structurally characterized by X-ray diffraction: the six-membered ring (germaoxaphosphorinene) conformation is a sofa form, with large folding along the Ge - C axis. A NMR study at various temperatures for 3a, 3a′, and 5a′ displays dynamic phenomenon including phosphorus and ring inversion. The low ΔG* values (respectively 18.2,13.7, and 13.2 kcal/mol) seem mainly due to substitution of phosphorus by the electropositive germanium and particularly to large steric effects; the 2,4,6-tri-tert-butylphenyl group lowers the inversion barrier by 5 kcal/mol when compared with the 2,4,6-triisopropylphenyl group.
