4183-87-3Relevant articles and documents
MODEL STUDIES IN THE TAXANE DITERPENE SERIES - Part. I
Cervantes, Humberto,Khac, Duc Do,Fetizon, Marcel,Guir, Frederic,Beloeil, Jean-Claude,Lallemand, Jean-Yves
, p. 3491 - 3502 (2007/10/02)
Photochemical cycloaddition of enol acetate 10a to cyclohexene led to a 3:1 mixture of the tetracyclic photoadducts A and B which, trough reverse aldol reactions, under mild alkaline conditions produced two compounds: a tetracyclic ketone 13 and a tricyclic diketone 14.Hydrolytic cleavage in methanolic hydrochloric acid of 15 and 16 resulting from irradiation of the enol ether 10b to cyclohexene gave rise to the rearranged tricyclic diketone 14 only.The trans stereochemistry 3α, 8β of the fused-ring system in 14, established by X-ray measurements, is different from the stereochemistry of the naturally occuring taxane derivatives.Ejus elementi compositionem quod vim habet in taxo baccata, photochimiae beneficio, quidam in exemplo simpliciore reddito experti sunt.Perincommode tamen accidit ut materiae ita quaesitae figura dissimilis sit ejus rei natura praebitae.
Photochemical and Thermal Rearrangements of Protonated 2,3-Homotropones
Childs, Ronald F.,Rogerson, Carol V.
, p. 4159 - 4166 (2007/10/02)
The 2-hydroxyhomotropylium cation 10 and 8-endo-methyl, 8-exo-methyl, 8,8-dimethyl, 1,8,8-trimethyl, and 3,8,8-trimethyl-2-hydroxyhomotropylium cations, 12, 11, 13, 14, and 15, respectively, were prepared by protonation of the corresponding 2,3-homotropones in FSO3H.On the basis of a comparison of the 1H NMR spectra of the 2-hydroxyhomotropylium ions with nonaromatic systems it is concluded that they can properly be regarded as homoaromatic cations.Ions 10, 11, 12, and 13 isomerizes when irradiated in FSO3H to give corresponding 1-hydroxyhomotropylium cations 19, 21, 22, and 23, respectively.The thermal isomerization of these ions has been investigated.Cation 22 was shown to isomerize to 21 at -39.5 deg C (k = 4.3*10-4s-1).An equilibrium was set up between these two ions consisting of 6percent 22 and 94percent 21 at 0 deg C.At higher temperatures 21 rearranged to protonated 1-phenylpropanal (k = 2.5*10-4s-1 at 37 deg C).The 8,8-dimethyl cation 23 isomerizes back to 13 (k = 3.1*10-4s-1 at -23 deg C), which underwent a further series of rearrangements to give eventually protonated 8,8-dimethylbicycloocta-3,6-dien-2-one (29).The symmetrical 8,8-dimethyl-4-hydroxyhomotropylium cation 32 was observed as an intermediate in the isomerization of 13 to 29.On the basis of the thermal isomerizations of 14 and 15 it was concluded that the 8,8-dimethyl-3-hydroxyhomotropylium cation must also be an intermediate in the conversions of 13 to 29 and 13 to 32.
