Sv
Use of Bieke's active maguesium permits to achieve two-step conversion of-the title dieues into respective allylic alcohols I-II.
Butadiene, iaoprene, xyrcene, and 60~18 other l,+dienes reic+with metallic magnesium; the respective addition compouuds have been recently prepared and their interactions with various electrophiles iuvestigated2*3. !l!he available data indicate that terminally substituted dienes (e.g.piperyled) react only reluctantly if at all. Therefore it was interesting to examine the Bieke*s active msgnesium (Hg*J4 which was already successfully used for the metalation of butadiene5. Our results on the reaction of Mg* with the title dienes in the presence of B( OBu?, are reported below.
We found that a slightly exothermic reaction takes place upon stirring a suspeusion of equiv.amounts of freshly prepared Mg*, diene and B( 0BunJ3 in !l!BP. The reaction mixture was refluxed for oa.l.5h to give, after oxidation with alkaline H202 solution and oolumu chromatography on alumina, zixture of alcohol8 (Scheme). Its components were isolated and purified by preparative GIG and/or columu chromatography followed by distillation. !l!heir structures were determined spectroscopically (BHB, lls, IX).
Under the above conditions, ieoureue gave a mixture of at least six monoterpenols 'll. The pairs of difficultly separableti-and B-gersniols 2,s and -nerols fi,6 were identified by direct comparison with authentic samples of o(-alcohog azd their E-ieomers. !l!he lamun "tail-to-tail" monoterpenol 2 aud itsa, B-isomer 2 were detected owing to coinoideuce of their PHB spectra with those reported8 for these compounds. Their coufiguration was confined by the CMB spectra (Soheme): the diaguostio signals of the allylio atozs gH3-C2 snd _&O for the both substances differ in their ch&emj3al shifts w 68 9 7.5 ppz, which is a value characteristic of Z,E isomers . Similarly, mrcene was converted into a mixture of viously uukuowu diterpenols z12, #&raniolQandthe preb.p.l20'/0.7 zm Bg; nB 1.4979; H+2901 Bg4:
1.59 (be, 9H, C&,', 1.67 (be, 6H, G33), 2.05 (I, 12H, C&>, 4.00 (be, 2H, C$O,, 5.02 (m, 3H, gC=C), 5.21 ppm (bt, J=7 Hz, IH, gC=C), aud El21 b.p.