Palladium-catalyzed formation and reactions of iodo- and bromosiloxane intermediates

Lu Zhou

Ohshita Joji

Mizumo Tomonobu

Journal of Organometallic Chemistry

Polysiloxanes are useful materials because of their functionality, such as high thermal stability, electrical resistance, and hydrophobicity. In this regard, we studied palladium-catalyzed formation of iodo-and bromopolysiloxanes from two types of hydrosiloxanes, alpha,omega-dihydropoly(dimethylsiloxane) (1) and cyclotetra(hydromethylsiloxane) (2), and their reactions. Treatment of 1 with mixtures of cyclic ethers or lactones and MeI or allylBr in the presence of a catalytic amount of PdCl2 gave the corresponding alpha,omega-bis(haloalkoxy and haloalkanoyloxy) poly(dimethylsiloxane)s in good yields, via iodo-and bromopoly(dimethylsiloxane) intermediates. Transformation of the iodobutoxy-terminal units in the resulting poly(dimethylsiloxane) into aminoalkoxy groups was examined. The formation of alpha,omega-diiodo- and dibromopoly(dimethylsiloxane)s from 1 was confirmed by spectrometric analysis as well as by quenching experiments with ethanol. A reaction of alpha,omega-dibromopoly(dimethylsiloxane) with 2,5-dilithiothiophene gave a polydimethylsiloxane-thiophene alternating polymer. Similar palladiumcatalyzed reactions of 2 with THF/MeI, THF/allylBr, and delta-valerolactone/allylBr afforded cyclo(halobutoxy- and bromobutanoyloxymethylsiloxane) s in moderate yields. This would provide a new strategy for the introduction of various substituents to the terminal positions of linear polysiloxane and to the cyclosiloxane core.

Polysiloxane

Boromosilane

Iodosilane

Palladium catalyst

Cyclic ether

Lactone

Chemistry [ 430 ]

eng

Elsevier Science SA

(c) 2012 Elsevier B.V. All rights reserved.

[ISSN] 0022-328X

[DOI] 10.1016/j.jorganchem.2011.10.012

[NCID] AA00704122

[DOI] http://dx.doi.org/10.1016/j.jorganchem.2011.10.012