Isolation of Silenolates (R₃Si)₂SiC(OLi)Ad with a Doubly Bonded Silicon Atom

Abstract

Die ersten Enolsilenolate, (tBuMe2Si)2SiC(OLi)Ad und (tBu2MeSi)2SiC(OLi)Ad, wurden synthetisiert und röntgenstrukturanalytisch charakterisiert. Im Unterschied zu organischen Enolaten, die ungeachtet ihrer Solvatisierung vorrangig in der Enolform vorliegen, ist bei Silenolaten Rechnungen zufolge die Enolform (links) in unpolaren Lösungsmitteln und die Ketoform (rechts) in stark solvatisierenden Lösungsmitteln bevorzugt. Ad=1‐Adamantyl.

Donor–Acceptor Adducts of a 1,3‐Disila‐2‐oxyallyl Zwitterion

“…21 This bond length is closer to that of the enol form (1.822 Å) than to the corresponding value of the keto form (1.926 Å) of the crystallographically characterized silenolates 20. 29 Indeed, Si3 displays just moderate pyramidalization, with a sum of angles of 355.5°. The Si1C2 bond to the NHC ligand is 2.000(2) Å, within the typical range for such interactions of the donor–acceptor type 13.…”

“…The chemical shift of the SiC unit reminiscent of cyclic silenes with donor substitution at the carbon atom 14. 21 With its pronounced zwitterionic character, 5 is best described as an silenolate‐type species, intermediate between the keto form prepared by Ottosson and co‐workers20 and the enol form reported more recently by the Apeloig and Zhivotovskii groups 29…”

Functional Disilenes in Synthesis

“…The NHC‐disilaoxyallyl adduct 149 is best described as a silenolate zwitterion, somewhere in between the keto form of a silenolate synthesized by Ottoson et al . and the enol form obtained by the Apeloig and Zhivotovskii groups …”

“…The NHC-disilaoxyallyl adduct 149 is best described as as ilenolate zwitterion, somewhere in between the keto form of as ilenolate synthesized by Ottoson et al [114] and the enol form obtained by the Apeloig and Zhivotovskii groups. [115] Since the recent disclosure of Grützmacher's improveds ynthesis of the phosphorus analogue of the cyanate anion,2phosphaetthynolate PCO À , [116] originally described by Becker et al, [117] its chemistry has flourished. The reactions of phosphaethynolate PCO À towards heteroallenes like carbodiimide, isocyanates and CO 2 have been reported by the Grützmacher and Goicoechea groups.…”

Synthesis of a Donor‐Stabilized Silacyclopropan‐1‐one

“…There have only been a few studies on 1-silenols and their derivatives, and only one stable 1-silenol ether has been reported. [25] Nevertheless, several related compounds, such as 2-silenolates [26] and Brook-type silenes, [27] have been synthesized and fully characterized. [24,28] Calculations demonstrated that the silenol 3 is considerably more stable than the corresponding keto tautomer, silanone 3 keto , by 23 kcal mol À1 , probably as a result of the efficient stabilization of the silene moiety by the adjacent phosphonio center (Scheme 4).…”