- Terpenes and Terpene Derivatives, XIX. - On the Selective Epoxidation of rac-β-Curcumene. Synthesis of 1-(4-Methyl-1,4-cyclopentadien-1-yl)ethanone
-
Epoxidation of rac-β-curcumene (1) yields a mixture containing the monoepoxides 2-4, and 6 in a ratio of 4:1:5:1 besides some other products.- Birch reduction of 17 gives only the hydrocarbon 18, even via the alkoxide. - The uncatalyzed Diels-Alder reaction of isoprene (10) with 3-butyn-2-one (11) leads to a mixture of the ketones 12-15 with a large amount of the 1,5-isomer 13 and the acetophenones 14 and 15.By TiCl4 catalysis the regioselectivity 12/13 can be enhanced to 94:6.
- Weyerstahl, Peter,Marschall-Weyerstahl, Helga,Scholz, Stefan
-
p. 1248 - 1254
(2007/10/02)
-
- Uncatalyzed Sigmatropic 1,5-Shift of Acyl Groups in the Thermolysis of 5-Acyl-5-methyl-1,3-cyclohexadienes
-
Four different 5-acyl-5-methyl-1,3-cyclohexadienes 1a-d (R=COOCH3, COCH3, COC6H5, CHO) have been shown to yield mixtures of 1,3-disubstituted cyclohexadienes 2-7 and 1,3-disubstituted aromatic product 8 upon thermolysis at 150-300 deg C in solution and at 350-500 deg C in the gas phase in a flow system.Two reaction pathways are considered for the rearrangement of the C-Skeleton.For the ester 1a 13C-isotopic substitution shows that products arise to 75-86percent through a 1,5-sigmatropic shift of the methoxycarbonyl group and to 14-25percent through a sequence of reaction steps involving a 1,7-H-shift reaction in an acyclic intermediate.For the more reactive compounds 1b-d isomerization is assumed to follow the 1,5-sigmatropic pathway exclusively.A kinetic study yields the following sequence for the migration tendency of acyl groups toward sigmatropic 1,5-shift: COOCH3 COCH3 COC6H5 CHO.
- Schiess, Peter,Dinkel, Rolf,Fuenfschilling, Peter
-
p. 787 - 800
(2007/10/02)
-