Electrochemical logic to synthesize disilanes and oligosilanes from chlorosilanes

Abstract

Oligosilanes are important compounds in industrial and synthetic chemistry. Here, we develop a general approach for the synthesis of linear and cyclic oligosilanes via the reductive activation of readily available chlorosilanes. The efficient and selective generation of silyl anion intermediates, which are arduous to achieve by other means, allows for the synthesis of various novel oligosilanes. In particular, this work presents a modular synthesis for a variety of functionalized cyclosilanes, which may give rise to materials with distinct properties from linear silanes but remain challenging synthetic targets. In comparison to the traditional Wurtz coupling, our method features milder conditions and improved chemoselectivity, broadening the functional groups that are compatible in oligosilane preparation. Computational studies support a mechanism whereby differential activation of two sterically and electronically distinct chlorosilanes are achieved in an electrochemically driven radical-polar crossover mechanism.

Iron‐Catalyzed Reductive C(aryl)—Si Cross‐Coupling of Diaryl Ethers with Chlorosilanes

“…On the basis of the above experimental results (see Supporting Information) and previous reports, [ 19‐25,84‐90 ] a possible mechanism for the reductive cross‐coupling reaction of 1a with 2a is tentatively proposed as shown in Scheme 4. A low‐valent iron species B would be formed by the reaction of 1a , FeCl 2 and i PrMgCl.…”

“…[ 1‐5 ] Therefore, the development of an efficient strategy to incorporate silicon motifs into organic molecules by forming C(aryl)—Si bonds is of great interest and much importance. Among possible approaches, the catalytic coupling reactions of silicon electrophiles represent a valuable strategy to construct C(aryl)—Si bonds, [ 6‐21 ] because silicon electrophiles like chlorosilanes [ 22‐25 ] are much more abundant and cheaper starting materials than silicon organometallic reagents [ 26‐30 ] and hydrosilanes. [ 31‐33 ] Although various catalysts have been reported for the couplings of silicon electrophiles with carbon nucleophiles, [ 11‐18 ] the reductive cross‐coupling of silicon electrophiles with carbon electrophiles in the formation of C(aryl)—Si bond has remained a great challenge.…”

Deep Electroreductive Chemistry: Harnessing Carbon- and Silicon-Based Reactive Intermediates in Organic Synthesis

“…67 We were interested in applying the principles of e-XEC to achieve Si−Si cross-electrophile coupling starting from chlorosilanes with distinct redox potentials and steric properties (Figure 11A). 68 For example, a chlorosilane with an aromatic stabilizing group (11-1) would preferentially undergo an overall two-electron reduction to form a silyl anion (11-4) in the presence of a di-or trialkylchlorosilane (11-3); the ensuing silyl anion would then selectively attack the sterically less encumbered di-or trialkylchlorosilane to complete the Si− Si bond formation (11-5). It should be noted that the electrochemical activation of chlorosilanes was previously explored in a few pioneering studies, 56,57 but the reaction scope and its synthetic applications were not established, particularly in the context of cross coupling and oligosilane synthesis.…”

Enabling Al sacrificial anodes in tetrahydrofuran electrolytes for reductive electrosynthesis

“…Scheme 2 illustrates an electrochemically driven silyl cross-electrophile coupling reaction. 44 The reaction has a notable high cell potential of 28-30 V during electrolysis when an Al sacricial anode is used in combination with TBAClO 4 / THF electrolyte (entry 5). Using TBACl as a co-supporting electrolyte results in a reduction in cell potential to the range of 10-14 V with improved yield of the disilane product (entry 6).…”

“…Currently, the use of an Al sacricial anode in THF-based electrolytes is commonly accompanied with extremely high overall cell potentials (>30 V) that inhibit electrolysis of the organic substrates. 15,[42][43][44] The escalation in voltage is frequently attributed to the formation of an oxide layer on the Al surface. Thus, to realize a wide application of Al sacricial anodes in THF-based electrolytes, the ability to control the Al interface is essential.…”