Reactions of dilithiobutadienes with monochlorosilanes: Observation of facile loss of organic groups from silicon

Selective Si-C(sp3) bond cleavage of a silyl-bridged amido alkyl ligand in an yttrium complex

Compared with Si-C(sp² and sp) bonds bearing neighboring π-bond hyperconjugative interactions, the activation of robust Si-C(sp³) bonds has proved to be a challenge. Herein, two distinct Si-C(sp³) bond cleavages have been realized by rare-earth-mediated and nucleophilic addition of unsaturated substrates. The reactions of Tp^Me2Y[κ²-(C,N)-CH(SiH₂Ph)SiMe₂NSiMe₃](THF) (1) with CO or CS₂ gave two endocyclic Si-C bond cleavage products, Tp^Me2Y[κ²-(O,N)-OCCH(SiH₂Ph)SiMe₂NSiMe₃](THF) (2) and Tp^Me2Y[κ²-(S,N)-SSiMe₂NSiMe₃](THF) (3), respectively. However, 1 reacted with nitriles such as PhCN and p-R'C₆H₄CH₂CN in a 1 : 1 molar ratio to yield the exocyclic Si-C bond products Tp^Me2Y[κ²-(N,N)-N(SiH₂Ph)C(R)CHSiMe₂NSiMe₃](THF) (R = Ph (4); R = C₆H₅CH₂ (6H); R = p-F-C₆H₄CH₂ (6F); and R = p-MeO-C₆H₄CH₂ (6MeO)), respectively. Moreover, complex 4 can continuously react with an excess of PhCN to form a Tp^Me2-supported yttrium complex with a novel pendant silylamido-substituted β-diketiminato ligand, Tp^Me2Y[κ³-(N,N,N)-N(SiH₂Ph)C(Ph)CHC(Ph)N-SiMe₂NSiMe₃](PhCN) (5).

(3 + 2)-Annulation of 1,3-N,Si-tetraorganosilane reagents TsHNCH2SiBnR1R2 with arynes for efficient synthesis of 3-silaindolines

1,3-N,Si-Tetraorganosilane reagents TsHNCH2SiBnR1R2 were developed as robust synthons to prepare 3-silaindolines via a Cs2CO3-promoted (3 + 2)-annulation reaction with arynes.

Advances in Synthesis of π-Extended Benzosilole Derivatives and Their Analogs

Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we have summarized several main approaches to construct (di)benzosilole derivatives and (benzo)siloles fused to aromatic five- and six-membered heterocycles.

1,4-Dilithio-1,3-dienes: reaction and synthetic applications

The development of organometallic reagents remains one of the most important frontiers in synthetic chemistry. Commonly used organometallic reagents (such as RLi and RMgBr) are typically monometallic compounds, although they aggregate in many cases. When two carbon-metal bonds are in the same molecule in close proximity, however, these two carbon-metal moieties may exhibit novel reactivity. In this Account, we outline our work on new reactions and synthetic applications of the organo-dilithio reagents 1,4-dilithio-1,3-butadienes. The 1,4-dilithio-1,3-butadienes can be accessed readily in high efficiency with a wide variety of substitution patterns on the butadienyl skeleton. The configuration has been predicted and demonstrated to favor a double dilithium bridging structure in both solution and solid states. The two Li atoms are bridged by a butadiene moiety and are in close proximity. By taking advantage of this unique configuration, we have developed useful and interesting synthetic methodologies. Three types of reactions of 1,4-dilithio-1,3-butadienes, termed dilithio reagents here, have been developed and are discussed. An intramolecular reaction is introduced in the first section. The reaction is a result of the intracooperative effect among the two C-Li moieties, the butadienyl bridge, and the substituents. A useful transformation from silylated 1,4-dilithio-1,3-butadienes to α-lithio siloles is described. Second, we discuss an intermolecular reaction that results from the intercooperative effect of the two C-Li moieties toward substrates. As an example of the formation of functionalized cyclic dianions from the linear dianions of the dilithio reagents and organic substrates, we describe the isolation and structural characterization of a novel type of cyclic dianion; that is, fully substituted oxy-cyclopentadienyl dilithium formed via the reaction of dilithio reagents with CO. We also describe diverse reactions of dilithio reagents with nitriles to form substituted pyridines, tricyclic 1-bipyrrolines, and siloles, demonstrating the remarkable effect of substituents on the butadienyl skeleton. Third, we discuss transmetalation of dilithio reagents to generate other organo-dimetallic compounds. This section focuses on organo-dicopper compounds and their reactivity toward the synthesis of strained ring systems, such as semibullvalenes and twisted four-membered rings, with the metal-mediated C-C bond-forming approach. In addition to these three representative reactions, other useful applications are also briefly introduced. The dimetallic 1,4-dilithio-1,3-butadienes and their transmetalated derivatives provide unique synthetic organometallic reagents that are very different from monometallic reagents, both in terms of reactivity and synthetic application. These organo-dimetallic reagents provide access to interesting and useful compounds that are not available by other means. Moreover, given the possibilities afforded, the study of organo-dimetallic and organo-polymetallic compounds should yield further synthetic applications in the near future.

9,9-Dimethyl-9-silafluorene

The title compound, C₁₄H₁₄Si, crystallizes with two almost identical mol­ecules (r.m.s. deviation = 0.080 Å for all non-H atoms) in the asymmetric unit. All atoms of the silafluorene moiety lie in a common plane (r.m.s. deviations = 0.049 and 0.035 Å for the two mol­ecules in the asymmetric unit). The Si—C_meth­yl bonds are significantly shorter [1.865 (4)–1.868 (4) Å] than the Si—C_aromatic bonds [1.882 (3)–1.892 (3) Å]. Owing to strain in the five-membered ring, the endocyclic C—Si—C angles are reduced to 91.05 (14) and 91.21 (14)°.

Synthesis of Multiply Substituted Alkylidene Silacyclohexadiene Derivatives via Palladium-Catalyzed Insertion of Alkynes into Alkylidene Silacyclobutenes

Palladium-catalyzed insertion of activated alkynes into silacyclobutene derivatives proceeded smoothly to afford exo-alkylidenesilacyclohexadiene derivatives of unique structure with diversified conjugation systems in high isolated yields. Interesting regioselectivity of insertion, which afforded only one regioisomer or a mixture of two or more regioisomers, was also observed.

Synthesis of silafluorenes by iridium-catalyzed [2 + 2 + 2] cycloaddition of silicon-bridged diynes with alkynes

[reaction: see text] Silicon-bridged 1,6-diynes underwent [2 + 2 + 2] cycloaddition with alkynes in the presence of an iridium(I)-phosphine catalyst to afford densely substituted silafluorene derivatives. Extended silafluorene skeletons were constructed by the [2 + 2 + 2] cycloaddition of tetraynes.