A new catalytic route to boryl- and borylsilyl-substituted buta-1,3-dienes

Vinyl-substituted boronates in the presence of complexes containing Ru-H bonds (preferably [Ru(CO)ClH(PCy(3))(2)], Cy: cyclohexyl) react regioselectively with terminal ethynes (involving silylethynes), albeit with the exception of phenylacetylene, to produce boryl- and borylsilyl-substituted buta-1,3-dienes with a preference for E,E-diene. The reaction opens a new catalytic route for the preparation of dienylboronates, and particularly dienylsilylboronates, that are functionalised building blocks in the synthesis of organic and natural products. The mechanism of this new reaction was proved to involve an insertion of alkyne into Ru-H bonds followed by an insertion of coordinated vinyl boronate into the Ru-C= bond and beta-hydrogen transfer to the metal to eliminate boryldiene or borylsilyldiene.     

A novel stereoselective carbon-chain extension reaction at the C-6 position of 1,6-anhydropyranose

6-Bromo-1,6-anhydro-d-mannose triacetate reacted with a variety of carbon nucleophiles such as allylsilane, silylacetylenes, propargylsilane, and aromatic compounds in the presence of silver triflate to give the corresponding chain extended products at C-6 in high exo-selectivities. The product obtained from the reaction with propargylsilane was efficiently transformed into a naturally occurring heptopyranose derivative found in bacterial lipopolysaccharide.     

Synthesis and properties of novel conjugated poly(silylacetylene silazane)s

A series of novel conjugated polymers, poly(silylacetylene silazane)s having different substituents, were prepared by ammonolysis of the corresponding α,ω‐dichlorosilyleneacetylene oligomers. The structures and properties of the poly(silylacetylene silazane)s were characterized by Fourier transform infrared, ¹H, ¹³C, ²⁹Si NMR, and elemental analyses, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and spectrofluorophotometry. The resulting polymers had good thermal properties and were moderately fluorescent. Their thermal stability was improved, and obvious red shift was observed when a phenyl substituent was attached on a silicon atom of polymers in the emission spectra. These polymers have the potential to be used as light‐emitting materials with good thermal stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2897–2903, 2004