RING-OPENING OF 1,2-BIS(TRIMETHYLSILOXY)-1,2-DIMETHYLCYCLOPROPANE WITH HYDROGEN BROMIDE AND BROMINE

The reaction of HBr and Br2 with 1:1 mixtures of cis- and trafw-1,2-bis(trimethylsiloxy)-1,2-dimethylcyclopropane (1 and 2) in CCl4 under anhydrous conditions at 0 °C was examined. In both cases cyclopropane cleavage occurred exclusively at the 1,3-bond. With HBr, 3-methyl-3-hydroxy-2-butanone (6), 3-bromo-3-methyl-2-butanone (7), and 1,3,3,4,6,6-hexamethyl-2,5,7-trioxabicyclo[2.2.1]heptane (8) were formed in yields of 38, 26, and 36%, respectively. With Br2 (dark), a 63% yield of 4-bromo-3-hydroxy-3-methyl-2-butanone (12) was obtained along with di-, tri-, and tetrabromo-substituted 1,3,3,4,6,6-hexamethyl-2,5,7-trioxabicyclo[2.2.1]heptanes. Both reactions produced bromotrimethylsilane (4) and hexamethyldisiloxane (5). © 1979, American Chemical Society. All rights reserved.