Wurtz coupling synthesis

Some oligomers were also isolated along with the polysilole when 1.2 equiv of the metal was used at room temperature for 1 day. Tamao and collaborators had earlier reported the Wurtz coupling synthesis of polysiloles.28d... 

Reported polymer yields of 60-80% are much higher than by the Wurtz-coupling synthesis, and the resulting polymers have M values in the range of 10 -10 depending on the amount of RLi used to initiate the polymerization. Furthermore GPC profiles reveal a monomodal distribution of molecular weights and polydispersities between 1.2 and 1.9. 

Most recently, a simple, mild, one-pot immobilization method was developed to attach the rigid rod-like helical polysilane, poly( -decyl-/-butylsilylene), via a siloxy linkage to hydrophilic quartz or mica substrate surfaces.28 195 Triethylamine was used as a catalyst to couple the Si-H and/or Si-OR termini of the dialkylpolysilane chains (which are generated during the course of Wurtz-type synthesis and workup)51,195 with the surface -OH groups. AFM, UV, and IR data were used to analyze the reactions. 

Polysilanes are polymers in which there is catenation of silicon, that is, where silicon atoms are bonded to each other in a continuous manner. Synthesis of polysilanes involves the Wurtz coupling of diorganodichlorosilanes with sodium metal (Eq. 2-239) [Baldus and Jansen, 1997 Corriu, 2000 Manners, 1996 Miller and Michl, 1989 West, 1986 West and Maxka,... 

The symmetrical Wurtz coupling has been found to give particularly good yields in the case of the higher alkane homologues. Selected illustrative examples (hexane, octane, decane and dodecane) are to be found in Expt 5.7. A related reaction is to be found in the synthesis of hexa- 1,5-diene (Expt 5.7, cognate preparation), which illustrates the symmetrical coupling of two molecules of allyl iodide by the action of sodium metal. 

Carbon-carbon bond forming reactions such as Wurtz coupling and 1,6-elimination, e.g. synthesis of [2.2] paracyclophane (Scheme 6.9). Here the lack of templation means that competing cyclisation and polymerisation is a significant problem. 

The application of the Wurtz coupling for the synthesis of [2.2](2,6)pyridinophane (85) from 2,6-bis(bromomethyl)pyridine (86) was already attempted in the fifties by Baker et al. [68]. Yet, the desired cyclophane could not be found. However, the intramolecular cyclization of 87 with phenyl Uthium or butyl lithium in ether led to in 3 and 28% yield, respectively [68]. The iwteraiolecular cyclization of 86 with phenyl lithium in dioxane gives a 9% yield of 85, too [69]. 

This route is useful for the synthesis of organolithium compounds, but is often hindered with the more reactive and heavier alkali metals because of the tendency toward Wurtz coupling (equation 2). 

Polysilylene Synthesis. Polysilylenes are synthesized by the Wurtz coupling reaction of dichlorodialkyl- or dichloroarylalkylsilanes with molten sodium in an aromatic solvent according to the following reaction ... 

A classical method using Na- or Li-liquid ammonia (Birch reduction conditions) is effective for reductive dehalogenations of aryl and vinylic halides, but it is not always successfully applied to alkyl halides, although cyclopropyl halides and bridgehead halogens are exceptions.Under such conditions, the reactions are often accompanied by side reactions, such as elimination, the Wurtz coupling reaction, cyclization and reduction of carbonyl compounds. An example, a synthesis of pentaprismane (1), is shown in Scheme 4. ... 

A third synthetic route that has been successfully exploited in the formation of five- and six-membered heterocycles has been studied in an attempted synthesis of a borirene derivative. Reaction of phenylboron dibromide with tolan gives a mixture of products resulting from both haloboration and phenylboration 109). A Wurtz coupling reaction of the former derivative could generate a borirene derivative... 

Silicon heterocycles with different ring sizes have been synthesized by variations of the organometallic Wurtz coupling reaction. The method requires synthesis of intermediate organosilicon derivatives that can involve several steps. 

Mistryukov, E. A. Ultrasound in organic synthesis. Electron-transfer catalysis in Li-TMSCI reductive benzene silylation and TMSCI Wurtz coupling. Mendeleev Common. 1993, 251. 

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