Nature of the carbonium ion. VII. Dehydronorbornyl cations from thiocyanate isomerizations

The use of lanthanides for solution structure determination of biomolecules by NMR. Evaluation of the methodology with EDTA derivatives as model systems

“…Furthermore, there are deviations exceeding the experimental uncertainties of the directions of each of the principal axes of from the initially chosen x, y, and z axes. The directions of the principal axes are not coincident among the ions for the 6 The experimental values are from 13X10 fits of 30 °C LIS data. The principal value of ' chosen is that with direction nearest the molecule-fixed z axis.…”

“…Assignments were not made for protons 22-41 of Yb-2 as discussed in the text so those distances are not listed. 6 Line width.…”

Nortricyclyl−Norbornenyl Cation System Accessed by Carbene Fragmentation

“…Fragmentation of carbene 6 differs from the solvolysis of brosylate 4a or the dediazoniation of 4e in that the product mixture from the fragmentation reaction is weighted toward norbornenyl chlorides (Table 2), whereas the latter two reactions are biased toward nortricyclyl chloride (Table 1). Similarly, Spurlock and Cox, who examined the rearrangement and isomerization of nortricyclyl and norbornenyl thiocyanates in MeCN at 150 °C, 31 reported that the product mixture obtained from the norbornenyl thiocyanate contained significantly more "unrearranged" exo-5-norbornenyl-2-isothiocyanate than obtained from the nortricyclyl thiocyanate. The reverse was true for nortricyclyl thiocyanate, where nortricyclyl isothiocyanate was produced in larger quantities than from the norbornenyl thiocyanate.…”

“…The reverse was true for nortricyclyl thiocyanate, where nortricyclyl isothiocyanate was produced in larger quantities than from the norbornenyl thiocyanate. Spurlock and Cox postulated ion pairs that differed in the position of the anion relative to the faces of the cation, much as we have invoked ion pairs which differ in the relative position of chloride, depending on whether the carbene precursor is 5 or 6 …”

Total Synthesis of (±)-Fasicularin via a 2-Amidoacrolein Cycloaddition

“…However, in our hands only trace amounts of fasicularin were observed. After considerable experimentation, we discovered that treatment of the mesylate 14 with tetrabutylammonium thiocyanate in toluene furnished fasicularin, albeit in poor yield (20%), accompanied by the isothiocyanate 15 (12%) and the elimination product 16 (28%). The spectral properties of our racemic fasicularin ( 1 ) were in agreement with those previously reported. 1a,b

3

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