In this study, a
variety of α,ω-bisacylpolysilanes
were synthesized via two synthetic protocols. The first method for
obtaining these compounds is based on the substitution reaction of
bromine either on silica gel or by the use of silver salts. Surprisingly,
instead of the expected bromine substitution product PhC(O)(SiMe2)2C(O)Ph 4a, we found the formation
of the diastereomer PhC(O)(SiMe2)2CBrPhOCBrPh(SiMe2)2C(O)Ph 4b indicating a more complex
reaction cascade. On the other hand, the phenylated compound 3b yielded the expected bromine substitution product PhC(O)(SiPh2)2C(O)Ph 4c. For the second protocol,
we utilized the Corey–Seebach approach to isolate other representatives
of this compound class. We found that the substituents at the α-silicon
atoms influence the selectivity of the dethioketalization. While the
ethylated and phenylated disilanes 5b,c yield
the expected bisacyldisilanes 6a,b, the
methylated disilane 4a undergoes a BF3-induced
Si–Si bond breakage followed by an intermolecular sila-aldol
reaction. This hitherto unknown sila-aldol reaction results in the
formation of the enantiomer PhC(O)SiMe2C(OMe)PhSiMe2F 6c in excellent yields. All isolated compounds
were analyzed by a combination of NMR spectroscopy, ultraviolet–visible
(UV–vis) spectroscopy, single-crystal X-ray crystallography,
and mass spectrometry. Furthermore, the photochemical pathways of
two representative examples (4b,c) were
examined.