Synthesis dehydrocoupling

Catalytic dehydrocoupling, as shown in reaction (3), was pioneered by Fink (6-10) and later studied by Andrianov et al (43). Although Fink described the synthesis of the first polysilazanes, (9) reaction (23), this route to oligo- and polysilazanes remained unexplored... 

There appear to be considerable steric demands involved in formation of the Si-N bond in reaction (28). Support for the importance of steric constraints in dehydrocoupling comes from studies on the synthesis of oligosilazanes from PhSiHj and NH3. When reaction (29) is run at 60°C, NMR and elemental analysis... 

The following reactions were performed to demonstrate the utility of transition metal dehydrocoupling for the synthesis of different types of polysilazanes and a novel polysiloxazane ... 

We have also explored the use of the dehydrocoupling reaction for the synthesis of preceramlc polysilazanes starting from the precursor MeNH-[H2SlNMe]x-H. As described above, MeNH-[H2SlNMe]X H Is produced by aminolysis of H2SiCl2 with MeNH2 under conditions where x 18-20 (Mn - 1150). 

The synthesis of comblike organoboron polymer was examined (see scheme 2) by dehydrocoupling polymerization of hydroborane monomers bearing an... 

To avoid problems associated with these polymer reactions, the direct synthesis of lithium borate polymer electrolytes37 was undertaken by dehydrocoupling polymerization using lithium mesitylhydroborate40 (scheme 7). 

Synthesis is typically by alkali metal-mediated coupling of dichlorosilanes or 1,2-dichlorodisilanes, although electrochemical coupling of chlorosilanes and dehydrocoupling of primary and secondary silanes also often lead to oligomeric (as opposed to high polymer) fractions. 

Kawakami, Y. Imae, I. Synthesis and Characterization of Siloxane-Containing Polymers Obtained by Dehydrocoupling Polymerization. In Synthesis and Properties of Silicones and Silicone-Modified Materials Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Van Dyke, M. E., Eds. ACS Symposium Series 838 American Chemical Society Washington, DC, 2003 pp 61-71. 

The condensation of diorganotin dihydrides with diorganotin diamides is another route to cyclic polystannanes. This method is especially useful for the high-yield synthesis of the dimethyl derivative (Me2Sn)g [eqn (10.5)], which cannot be obtained by the dehydrocoupling process. 

A less explored area of transition metal catalysis involves bond formation between Group 14 elements and nitrogen. In direct analogy to previously discussed areas of research, silicon-nitrogen bonds can be formed by dehydrocoupling, hydrosilylation, and dehydrogenative silylation. The compounds produced are valuable for use in organic synthesis or as polymer precursors to silicon nitride ceramics. 

Mu, Y. Harrod, J. F. Synthesis of Poly(methylsilyene) by Catalytic Dehydrocoupling with Cp2MMe2 (M = Ti, Zr) Catalysts, (J. F. Harrod, R. M. Laine, Eds.) Inorganic and Organometallic Oligomers and Polymers, Kluwer Academic Publishers, Netherlands, 1991. p. 23. 

Aryl halides, carbonylation of, 271-272 Arylboronates, synthesis of, 223-226 Arylsilanes, dehydrocoupling, 21... 

Dehydrocoupling (also referred to as dehydrocondensation) provides a versatile route to the synthesis of E-E bonds. The generalized dehydrocoupling reaction is shown in Eq. (1). 

A wide range of catalysts have been reported for dehydrocoupling of OH-containing compounds with silanes. These include acids and bases and both homogeneous and heterogeneous transition-metal catalysts. Such reactions can be useful in organic synthesis (protection of OH groups), in... 

It is clear that catalytic dehydrocoupling is a versatile technique for the synthesis of E-E and E-E bonds. The scope of the methodology, in terms of the types of reactions that can be carried out and the selectivities that are possible, has been broadly established. There is still much to be done in unequivocally establishing the mechanisms and the types of catalytic intermediates involved. 

Ruthenium carbonyl complexes, for example, Ru3(CO) 12 can be used as catalysts for the synthesis of oligosilazanes via dehydrocoupling of Si-H bonds with H-N bonds (Eq. 117) [185]. 

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