Exploring Planar‐Chiral Amino Siloxides

Abstract

We present the synthesis, structure, and exemplary reactivity of siloxides with a planar-chiral N,N-dimethylaminomethylferrocene backbone. Several zinc complexes based on the racemic as well as the enantiomerically pure silanol were synthesized in the presence of water and crystallographically characterized, and their behavior in solution was examined. The chiral probe present in this system is a valuable tool for identifying the structure in solution. Furthermore, the zinc siloxides exhibit a comparable reactivity to the corresponding silanols. Therefore, they can be regarded as "masked" silanols, especially when the silanols are preparatively inaccessible.

Crystal structures of [(N,N-dimethylamino)methyl]ferrocene and (R p,R p)-bis{2-[(dimethylamino)methyl]ferrocenyl}dimethylsilane

“…Many applications based on 1 have been established by our research group: it is an inexpensive non-chiral analogue of Ugi's amine, therefore the desymmetrization must be implemented by the chiral auxiliary (R,R)-tetramethyl-1,2-cyclohexanediamine (TMCDA) with yields in high stereoselectivity (Steffen et al, 2013). One application of the 1,2-disubstituted ferrocenes based on 1 is the formation of racemic and enantiomerically pure siloxides of zinc, whereby disiloxanes ISSN 2056-9890 can be synthesized while avoiding condensation reactions (Golz et al, 2017). Another application is the kinetically controlled asymmetric synthesis of silicon-stereogenic methoxy silanes using a planar chiral ferrocene backbone based on 1.…”

Influence of Amino Functions on the Coordination Ability of Silyl Ethers and Disiloxanes

“…Understanding the interactions of Si–O–Si units with Lewis acids in general and metal centers in particular is of great interest, especially with regard to challenging siloxane bond cleavage reactions and the development of silicon analogues of crown ethers and cryptands . In the past few years, the provision of molecular model systems for studying Si–O–Al and Si–O–Zn , structural motifs has also become a fascinating research area. In theoretical studies to determine the nature of the Si–O bond in siloxanes, Weinhold and West rely on a pronounced resonance view of the Si–O–Si bond in which negative hyperconjugative interactions between oxygen lone electron pairs and vicinal antibonding σ*-orbitals are regarded as the reason for the low basicity of the Si–O–Si unit compared to the ether (C–O–C) unit .…”

Design, synthesis, characterization, and aging properties of a new end‐capped three‐dimensional high‐refractive index hybrid organic–inorganic polysiloxane

“…41 This reaction has also been used for the preparation of AB 2 type monomers in the synthesis of hyperbranched poly(aminopropyl)alkoxysiloxanes and their derivatives, 42 and furthermore for the preparation of (ferriomethyl) silanols and related structures. 43,44,45 End-capping of linear polysiloxanes such as poly(dimethylsiloxanes), dimethylsiloxane-based copolymers, poly(aryl-alkyl)siloxanes or acrylate functionalized dimethylsiloxane-based copolymer with ClTMS is consequently well known. Transformation of terminal OH groups in poly(dimethylsiloxanes) to corresponding OTMS has resulted in increasing the stability of the linear polymer, 46 and many trimethylsilyl-terminated linear polysiloxanes are commercially available.…”