Syntheses and Properties of Sila-functional Oligosiloxanes: A Simple and Practical Method for the Synthesis of 1,1,3,3-Tetra-isocyanato-1,3-disubstituted Disiloxane
Syntheses and Properties of Sila-functional Oligosiloxanes: A Simple and Practical Method for the Synthesis of 1,1,3,3-Tetra-isocyanato-1,3-disubstituted Disiloxane
The titled disiloxanes with the substituents of methyl, vinyl, phenyl, and isocyanato group were synthesized in excellent yields by a vapor phase hydrolysis of the corresponding isocyanatosilanes using a simple reaction apparatus. The process would provide a practical method for the syntheses of not only the sila-functional disiloxanes but also the other oligosiloxanes with various functional groups.
The syntheses of the titled oligosiloxanes by controlled hydrolysis of the corresponding isocyanatosilanes under vapor phase or in THF (or THF/ether) were investigated. The vapor phase hydrolysis of RSi(NCO)3 (R = Me, Vinyl) with a water–1,4-dioxane vapor gave the disiloxanes [R(OCN)2Si]2O in yields of 85% (R = Me) and 90% (R = Vinyl). Further vapor phase hydrolysis of the disiloxanes provided the linear tetrasiloxanes NCO[SiR(NCO)O]3SiR(NCO)2 in yields of 71% (R = Me) and 69% (R = Vinyl). The cyclotetrasiloxanes [R(OCN)SiO]4 were synthesized in yields of 12% (R = Me) and 33% (R = Vinyl) or 24% (R = Me) and 58% (R = Vinyl) by hydrolysis of the disiloxanes or of the linear tetrasiloxanes in THF, respectively. On the other hand, the linear tetrasiloxanes OCN[SiR(OPri)O]3SiR(OPri)(NCO) were obtained in yields of 50% (R = Me) and 56% (R = Vinyl) by hydrolysis of [R(OCN)(PriO)Si]2O prepared from RSi(OPri)(NCO)2 under mild conditions in THF/ether, while the cyclic tetrasiloxanes [R(PriO)SiO]4 were afforded in the yield of 61–62% by hydrolysis of the disiloxanes under more severe conditions in THF.