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Relevant academic research and scientific papers

Siloxa-bridged-cyclophanes featuring benzene, thiophene and pyridine units

Two octamethyldisiloxa-bridged [3.3]cyclophanes (1 and 2) and a dodecamethyltrissiloxa-bridged [3.3.3]-cage compound (3) were prepared by hydrolysis of the chlorosilyl monomers. This general route was also employed for the preparation of two octamethyldisiloxa-bridged [3.3]heterophanes featuring two thiophene (14) or pyridine (17) moities.

Efficient zirconocene-coupling of silicon-substituted diynes to polymers and macrocycles

The zirconocene-coupling of diynes with internal silicon substituents, MeC≡CMe2SiArSiMe2C≡CMe (1: Ar = 1,4-C6H4; 2: Ar = 1,3-C6H4; 3: Ar = 1,3-C6H4; 3: Ar = 4,4'-C6H4C6H4), generates regiospecific polymers containing zirconacyclopentadiene in the main chain (5-7). These organometallic polymers hydrolyze cleanly to butadienediyl polymers of the type [Me2SiArSiMe2CH = CMeCMe = CH](n) (11-13), and polymer 5 reacts with iodine to give the iodine-containing polymer [1,4-Me2SiC6H4SiMe2C(I)=CMeCMe=C(I)](n) (14). The organometallic polymers undergo facile and high-yield degradations to macrocycles under mild conditions (refluxing tetrahydrofuran solution). The size and shape of the resulting macrocycles depend upon the nature of the diyne spacer group. Thus, polymers 5 and 7 containing parallel diyne units convert to the trimeric macrocycles [Me2SiArSiMe2C4Me2ZrCp2]3 (15: Ar = 1,4-C6H4; 24: Ar = 4,4'- C6H4C6H4), while polymer 6 gives the dimeric macrocycle [1,3- Me2SiC6H4SiMe2C4Me2ZrCp2]2 (18). The dimeric macrocycle [Me2SiC6H4SiMe2C6H4SiMe2C4Me2ZrCp2]2 (20) was obtained directly from the zirconocene coupling of Me2Si[(1,4-C6H4)- SiMe2(C≡CMe)]2 (4) by heating the reaction mixture to reflux. In a similar manner, the diyne Me2Si(C≡CMe)2 was converted in high yield to the hexameric macrocycle [Me2SiC4Me2ZrCp2]6 (22). The macrocycles 15, [1,4-Me2SiC6H4SiMe2C4Me2H2]3 (16), and 18 were characterized by single-crystal X-ray crystallography. Molecules of 15 adopt a nearly planar C3 macrocyclic structure with a cavity described by an average transannular Si···Si distance of 13.2 A?, while the hydrolyzed macrocycle 16 has a chair conformation. This conformation change results from conversion of cis diene groups in the zirconacyclopendiene fragments to trans diene groups in 16. The high- yield formation of macrocycles apparently results from the reversible nature of the alkyne-coupling reaction, which allows for a low-energy pathway to the smallest macrocycle possessing minimal ring strain.

Silylative Decarbonylation: A New Route to Arylsilanes

A new synthetic procedure for the preparation of aromatic chlorosilanes via the palladium-catalyzed reaction of methylchlorodisilanes and aromatic acid chloride is described.The silylative decarbonylation process is solventless, can utilize low metal catalyst loadings (500-1000 ppm Pd), is carried out under moderate conditions (145 deg C), and selectively gives aromatic chlorosilanes in good yield, generally 60-85percent.The procedure is tolerant of a variety of aromatic substituents, for example, alkyl, halo, nitro, cyano, imide, acid anhydride, etc., and the synthesis ofseveral new substituted aromatic chlorosilanes containing benzoyl chloride and phthalic anhydride moieties is described.Chloromethyldisilane starting reagents are available from the direct reaction of methyl chloride and silicon, making this methodology an attractive synthetic route to functionalized aromatic chlorosilanes.