Stereocontrolled Syntheses of Functionalized cis- and trans-Siladecalins

Abstract

We report the synthesis of both diastereomers of an all-silicon analog of decalin. Carbocyclic decalin is a ubiquitous bicyclic structural motif. The siladecalin synthesis provides materials functionalized with either Si−Ph or Si−H groups, versatile entry points for further chemical diversification. The synthesis of silicon-stereogenic silanes is significantly less precedented than the synthesis of asymmetric carbon centers, and strategies for control of relative stereochemistry in oligosilanes are hardly described. This study offers insights of potential generality, such as the epimerization of the cisisomer to the thermodynamically downhill trans-isomer via a hypothesized pentavalent intermediate. Decalin is a classic example in the conformational analysis of organic ring systems, and the carbocyclic diastereomers have highly divergent conformational profiles. Like the carbocycle, we observe different conformational properties in cis-and trans-siladecalins with consequences for NMR spectroscopy, optical properties, and vibrational spectroscopy. This study showcases the utility of targeted synthesis for preparing complex and functionalized polycyclic silanes.

An Electroreductive Approach to Silyl Radical Chemistry via Strong Si–Cl Bond Activation

“…A diverse array of chlorosilanes proved to be effective for the construction of value-added organosilanes (24)(25)(26)(27)(28)(29). In particular, dimethylsilane (24), vinyldimethylsilane (26), and allyldimethylsilane (27) led to products that could be used as monomers for silicon-containing polymers.…”

“…19 Furthermore, the incorporation of disilane groups vicinally to an alkene (25,28) demonstrated the potential utility of this reaction for the preparation of parallel single-molecular silicon wires for materials and electronic applications. 20 Chlorotrimethylgermane could also react to furnish product 29. The success and limitation of our reaction scope piqued our interest in investigating the reaction mechanism with the objective of expanding the reactivity to other synthetically useful transformations.…”

An Electroreductive Approach to Silyl Radical Chemistry via Strong Si–Cl Bond Activation

“…A diverse array of chlorosilanes proved to be effective for the construction of value-added organosilanes (24)(25)(26)(27)(28)(29). In particular, dimethylsilane (24), vinyldimethylsilane (26), and allyldimethylsilane (27) led to products that could be used as monomers for silicon-containing polymers.…”

Isolation of a Cyclopentasilane from Magnesium Reduction of a Linear Hexasilane

“…We previously reported the stereocontrolled synthesis of cis-and transsiladecalins where a key intermediate was 1,2-dichlorocyclosilane 1 a (Scheme 1a). [25] To further explore the potential applications of 1 a, we envisaged reductive dimerization via a postulated intermediate disilene 2 a to yield 3 a, a strained permethylated silicon analogue of dodecahydrobiphenylene (Scheme 1b). Embedding silicon in a four-membered ring results in compelling properties such as enhanced Lewis acidity, [26] unusual conductance [27] and visible light emission, [28,29] as well as utility in ring-opening polymerization.…”

“…In our earlier siladecalin synthesis, linear hexasilane 4 a was straightforwardly reduced to cyclohexasilane 5 a using Mg powder (Scheme 2a) [25] and our prior synthesis of 4 a was readily adapted to provide the tert-butyl analog 4 b (Scheme 2b). tert-Butyl(chloro)diphenylsilane (TBDPSCl) is a common alkoxy protecting group in organic synthesis.…”