1,1,3,3-Tetramethyl-disiloxane → Trisiloxane, 1,1,3,3,5,5-hexamethyl-

Participants

Reaction Conditions

Reaction Steps

Allyloxybenzophenone 1 (200 g, 840 mmol) was dissolved with warming in THF (150 mL, EM Science) and charged to an addition funnel placed on a 2L four-necked flask equipped with a mechanical stirrer, reflux condenser and internal temperature probe under a dry air purge. To the reaction vessel was added 1,1,3,3-tetramethyldisiloxane (740 mL, 4.18 mol, Hanse Chemie) and THF (100 mL). The internal pot temperature was raised to 50° C., at which point chlorotris(triphenylphosphine) rhodium (“Wilkinson's catalyst”, 22 mg, 11 ppm based on mass of allyloxybenzophenone 1, Aldrich Chemcial) was added to the pot along with a portion (5 mL) of the 4-allyloxybenzophenone/THF solution. The internal reaction temperature was raised to 60° C., at which point the 4-allyloxybenzophenone solution was added to the reactor pot over the course of 45 min. The internal temperature of the reaction was held between 60–65° C. during the course of the addition, which is exothermic. After the addition was complete, the reaction was stirred at 60° C. for an additional 15 min., at which point no starting material was present by GC analysis. The reaction was allowed to cool to 35° C., and activated carbon (3 lab scoops, Aldrich Chemical) was added. The resulting slurry was stirred for 30 min., then filtered to yield a pale yellow solution. Solvent was removed from the product in vacuo to yield a yellow oil (329 g, 104% due to presence of ˜10 mol % 1,1,3,3,5,5-hexamethyltrisiloxane in the commercial grade 1,1,3,3-tetramethyldisiloxne starting material; i.e. the reaction is essentially quantitative). The product exhibited acceptable 1H, 13C & 29Si NMR, UV-Vis and FT-IR spectral characteristics.

Provenance & Evidence