5489The data in Table I as well as the data for allyl vinyl ether 1 suggest that the [ 1,3] rearrangement products observed may arise via dissociated ions followed by recombination. Note that the vinyl ether derived from verbenol (entry 5) gives rise to the [1,3]-rearranged product with exclusive inversion of configuration at the allylic carbon atom, suggesting that the [1,3] rearrangement is concerted. However, the formation of the observed product can also be rationalized via dissociated ions followed by recombination from the least hindered face of the molecule. In order to determine to what extent allyl vinyl ethers ionize in the presence of 3.0 M lithium perchlorate-diethyl ether, a crossover experiment was carried out employing allyl vinyl ethers 4 and 5, each 0.1 M in 3.0 M lithium perchloratediethyl ether. After 1.5 h a t ambient temperature, there was obtained, in excellent yield, a mixture of aldehydes 6 and 7 and ketones 8 and 9 in a ratio of 1.0:1.8:1.5:1.6, suggesting that dissociated ions are involved. 4 5 6 7 8 9(6) Acetone was employed as the solvent because in diethyl ether the reaction rates for the [1,3] rearrangement were too fast to be measured by 'H NMR. In addition, tetra-n-butylammonium perchlorate is insoluble in ether. Reactions were carried out 0.2 M in substrate in sealed NMR tubes at 22 OC. Note that the reaction of 10 in 3.0 M LiCI04-Et20 gave 14% after 1 h to an 86% isolated yield of aldehyde 11.
Die Umsetzung von Veratrol (I) mit CH2O in saurem Medium führt zum Cyclotriveratrylen (IIa) , dessen Demethylierung mit BBr3 in DMF unter N2 und Reaktion mit NaH das Na‐Salz (IIb) liefert.
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