Copyrolysis of 1,1-Dimethyl-1-Silacyclobutane and Acrolein.

摘要

Copyrolysis of 1, 1-dimethyl-1-silacyclobutane and acrolein at 600 C in the gas phase yields ethylene, hexamethylcyclotrisiloxane (trimer), octamethylcyclotetrasiloxane(tetramer), 1,3-butadiene, 3-cyclohexene-1-carboxaldehyde, 1,1-dimethyl-2-oxa-1-sila-3-cyclohexene, and 1,1,3,3-tetramethyl-2,4-dioxa-1,3-disila-5-cyclooctene. Formation of the products can be accounted for in terms of initial competing (2+2) and (2+4) cycloaddition reactions between acrolein and (CH3)2Si=CH2) (formed by pyrolysis of 1,1-dimethyl-1-silacyclobutane). The (2+4) reaction yields 1,1-dimethyl-2-oxa-1-sila-3-cyclohexene. The (2+2) reaction yields an unstable silaoxetane intermediate which decomposes to yield 1,3-butadiene and dimethylsilanone. Cyclooligomerization of the reactive dimethylsilanone yields trimer and tetramer. Insertion of dimethylsilanone into the Si-O single bond of 1,1-dimethyl-2-oxa-1-sila-3-cyclohexene yields 1,1,3,3-tetramethyl-2,4-dioxa-1,3-disila-5-cyclooctene. 3-Cyclohexene-1-carboxaldehyde is formed by a Diels-Alder reaction between 1,3-butadiene and excess acrolein under the reaction conditions.