Carbenium ion trapping using sulfonamides: an acid-catalysed synthesis of pyrrolidines by intramolecular hydroamination
作者:Charlotte M. Griffiths-Jones (née Haskins)、David W. Knight
DOI:10.1016/j.tet.2010.03.107
日期:2010.6
Cyclisations of homoallylic sulfonamides proceed smoothly via carbenium ion generation using trifluoromethanesulfonic (triflic) acid, the ease of cyclisation being directly related to the ion stability to give good to excellent yields of the corresponding pyrrolidines. Both toluene- and nitrophenyl-sulfonyl groups are suitable for all substrates tested whereas the corresponding carbamates are only useful in cases of tertiary and highly stabilised carbenium ions. Polyene-derived sulfonamides can also be cyclised to the corresponding polycyclic systems in remarkably high yields, in reactions reminiscent of related cascades encountered in terpene biosynthesis. (C) 2010 Elsevier Ltd. All rights reserved.
Bridged (β-alkoxyalkyl)CoIII(salen) complexes by intramolecular alkoxycobaltation of unactivated alkenes: new models for coenzyme B12
作者:Rolf Blaauw、Irene E. Kingma、Jan H. Laan、Juul L. van der Baan、Sijbe Balt、Martinus W. G. de Bolster、Gerhard W. Klumpp、Wilberth J. J. Smeets、Anthony L. Spek
DOI:10.1039/b000196l
日期:——
but-2-en-1-yl (6c), but-3-en-1-yl (6d)] react with oxygen and alcohols to give organocobalt(III) complexes containing a β-alkoxy-substituted three- or four-carbon bridge between cobalt and the equatorial ligand. NMR and UV–VIS spectroscopic studies show that product formation is a three-stage process involving (1) oxidation of cobalt(II) to produce an (alkoxo)cobalt(III) complex, (2) intramolecular interaction