Bromoethene → alpha-Irone

Participants

Reaction Conditions

Reaction Steps

A solution of 50 g (0.26 mol) of α-ionone in 150 ml of tetrahydrofuran was allowed to drop over a period of 20 minutes into a Grignard solution, which was cooled to 0° C. and which had been prepared from 9.72 g (0.4 mol) of magnesium shavings in 75 ml of tetrahydrofuran and 44.9 g (0.42 mol) of vinyl bromide in 180 ml of tetrahydrofuran, in such a manner that the temperature lay between 15° C. and 20° C. Subsequently, the mixture was stirred at room temperature for a further 3 hours and worked-up as described in Example 8. There were obtained 54.5 g of crude product which contained above 92% 9-vinyl-α-ionol according to GC and which was further processed directly in this form. In a manner analogous to the epoxidation of α-irone (Example 4), from 53.2 g (0.242 mol) of 9-vinyl-α-ionol there were obtained 59.0 g of crude 9-vinyl-α-ionol epoxide of which 58.0 g were dissolved together with 26.5 g (0.13 mol) of aluminium isopropylate in 175 ml of isopropanol. By following the procedure described in Example 1 there were obtained 57 g of a crude product. From this crude product there were obtained by distillation over a 20 cm Widmer column 15.0 g (26%) of olfactorily good product of boiling point 73°-74° C./0.3 mmHg which contained above 85% 20a and 20b in the approximate ratio of 3:2. In addition, there were present small amounts of the corresponding 7-oxa-bicyclooctane 20c. ##STR33##

Provenance & Evidence