Hexamethyltrisiloxane-1, 5-diol

Hexamethyltrisiloxane-1,5-diol A Versatile Precursor for Linear, Cyclic, and Spirocyclic Siloxanes 425... 

The pentasiloxane was formerly synthesized conveniently by cocondensation of dichlorodimethylsilane and chlorodimethyl-silane in a low yield. A paper reported that the compound can be synthesized by cross-condensation of hexamethylcyclotrisiloxane and excess dimethylchlorosilane with water treatment (3). Herein, we show a versatile synthetic method of terminal-functional pentasiloxane from pure hexamethyltrisiloxane-1, 5-diol. 

Hexamethyltrisiloxane-1,5-diol, chlorodimethylsilane, dry pyridine, dry THF, hexane, anhydrous magnesium sulfate. 

The spirocyclic siloxane consisting of two cyclotetrasiloxane rings was first reported by a Russian group in low yield (8,9). Also, synthesis by vacuum flash pyrolysis was described, but again in low yield (10,11). Herein, we describe a convenient synthetic method of compounds derived from hexamethyltrisiloxane-1,5-diol in moderate yields. 

Hexamethyltrisiloxane- 1,5-diol, silicon tetrachloride, triethylamine, dry ether, hexane, anhydrous sodium sulfate. 

An argon-purged three-necked 200 mL round bottom flask was charged with 1,1,3,3,5,5-hexamethyltrisiloxane-1,5-diol (4.98 g, 20.8 mmol), and triethylamine (4.21 g, 41.6 mmol) in dry ether (40 mL). An ether (43 mL) solution of silicon tetrachloride... 

An argon-purged three-necked 500 mL round bottom flask was charged with chlorodimethylsilane (21.8 g, 91.7 mmol), dry pyridine (22.6 g, 286 mmol), and dry THF (135 mL). A THF (50 mL) solution of l,l,3,3,5,5-hexamethyltrisiloxane-l,5-diol (22.0 g, 91.5 mmol) was added dropwise within 1.5 h and the solution was stirred for 20 h. The resulting mixture was diluted with hexane, and the organic phase was washed successively with water and brine and dried with anhydrous MgS04. The solvent was removed by rotary evaporator. Vacuum distillation of the crude product (bp 42°C/80 Pa) afforded the pure product as a colorless liquid yield 58.4 g (88%). 

An argon-purged, three-necked 300 mL round flask was charged with l,l,3,3,5,5-hexamethyltrisiloxane-l,5-diol (10.1 g, 42.0 mmol), triethylamine (9.47 g, 93.6 mmol), and dry ether (100 mL). 

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