Synthesis of ladder and cage silsesquioxanes from 1,2,3,4-tetrahydroxycyclotetrasiloxane

The versatility of cis,cis,cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisopropylc yclotetrasiloxane (I) as a precursor of cage and ladder siloxanes is presen ted. Compound I reacted with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in pyridine to give 1,3,5,5,7,7,9,11,13,13,15,15-cis-cisoid-cis-dodecaisopr opyltricyclo[9.5.1.1(3,9)] (2) in 20% yield. The reaction proceeded with re tention of the configuration of the silicon atoms, and only syn-type isomer was obtained. The reaction of 1 with 1,1,3,3-tetrachloro-1,3-diisopropyldi siloxane in pyridine produced hexakis(isopropylsilsesquioxane) (T-6) (3) in 25% yield. Treatment of 1 with dicyclohexylcarbodiimide (DCC) as dehydrati ng reagent led to the formation of octakis(isopropylsilsesquioxane) (T-8) ( 4) in 45% yield. The crystal structures of 2, 3, and 4 are reported.