Tungsten-Mediated Selective Ring Opening of Vinylcyclopropanes

The complexes TpW­(NO)­(PMe₃)­(L), where L = 2<i>H</i>-phenol, 2<i>H</i>-<i>p</i>-cresol, 2<i>H</i>-5,6,7,8-tetrahydro-2-naphthol, 2<i>H</i>-<i><i>N,N</i>-</i>dimethylanilinium were cyclopropanated using Simmons–Smith conditions. Cyclopropanated derivatives of 2<i>H</i>-<i>N,N</i>-dimethylanilinium were selectively ring-opened with HOTf/MeCN to form allylic species, which could be coupled with various nucleophiles. The nucleophilic addition occurs <i>anti</i> to the metal fragment, as determined by X-ray crystallography. Moreover, the cyclopropane ring opening occurs regioselectively, owing to the stabilization of the allylic cation by the metal fragment. The resulting ligands can, in some cases, be removed from the metal by oxidative decomplexation using ceric ammonium nitrate (CAN)

Tungsten-Mediated Selective Ring Opening of Vinylcyclopropanes

The complexes TpW­(NO)­(PMe₃)­(L), where L = 2<i>H</i>-phenol, 2<i>H</i>-<i>p</i>-cresol, 2<i>H</i>-5,6,7,8-tetrahydro-2-naphthol, 2<i>H</i>-<i><i>N,N</i>-</i>dimethylanilinium were cyclopropanated using Simmons–Smith conditions. Cyclopropanated derivatives of 2<i>H</i>-<i>N,N</i>-dimethylanilinium were selectively ring-opened with HOTf/MeCN to form allylic species, which could be coupled with various nucleophiles. The nucleophilic addition occurs <i>anti</i> to the metal fragment, as determined by X-ray crystallography. Moreover, the cyclopropane ring opening occurs regioselectively, owing to the stabilization of the allylic cation by the metal fragment. The resulting ligands can, in some cases, be removed from the metal by oxidative decomplexation using ceric ammonium nitrate (CAN)

[4 + 2] Cyclocondensation Reactions of Tungsten–Dihydropyridine Complexes and the Generation of Tri- and Tetrasubstituted Piperidines

A new method for the preparation of functionalized piperidines is described in which various dihydropyridine (DHP) complexes of {TpW(NO)(PMe₃)} that are derived from pyridine–borane undergo [4 + 2] cyclocondensation with enones, enals, nitrosobenzene, and several isocyanates to form [2.2.2] bicyclic species. In several cases the diazabicyclooctene products derived from DHP complexes and isocyanates can be further elaborated into novel <i>syn</i>-2,5-disubstituted and 2,3,6-trisubstituted piperidinamides

[4 + 2] Cyclocondensation Reactions of Tungsten–Dihydropyridine Complexes and the Generation of Tri- and Tetrasubstituted Piperidines

A new method for the preparation of functionalized piperidines is described in which various dihydropyridine (DHP) complexes of {TpW(NO)(PMe₃)} that are derived from pyridine–borane undergo [4 + 2] cyclocondensation with enones, enals, nitrosobenzene, and several isocyanates to form [2.2.2] bicyclic species. In several cases the diazabicyclooctene products derived from DHP complexes and isocyanates can be further elaborated into novel <i>syn</i>-2,5-disubstituted and 2,3,6-trisubstituted piperidinamides

[4 + 2] Cyclocondensation Reactions of Tungsten–Dihydropyridine Complexes and the Generation of Tri- and Tetrasubstituted Piperidines

A new method for the preparation of functionalized piperidines is described in which various dihydropyridine (DHP) complexes of {TpW(NO)(PMe₃)} that are derived from pyridine–borane undergo [4 + 2] cyclocondensation with enones, enals, nitrosobenzene, and several isocyanates to form [2.2.2] bicyclic species. In several cases the diazabicyclooctene products derived from DHP complexes and isocyanates can be further elaborated into novel <i>syn</i>-2,5-disubstituted and 2,3,6-trisubstituted piperidinamides

Friedel–Crafts Ring-Coupling Reactions Promoted by Tungsten Dearomatization Agent

The complexes TpW­(NO)­(PMe₃)­(L), where L = phenol, <i>N,N-</i>dimethylanilinium, or naphthalene, undergo protonation followed by addition of an aromatic nucleophile. The addition of aromatic molecules occurs at the para carbon of the phenol or aniline ring or the beta carbon of the naphthalene. The addition occurs anti to the metal fragment, as determined by X-ray crystallography. In the case where L = phenol or <i>N,N-</i>dimethylanilinium, treatment of the bound arene with an electrophilic heteroatom followed by an aromatic nucleophile sets two stereocenters, with both additions occurring anti to the metal. The resultant ligands have been removed from the metal by oxidative decomplexation using ceric ammonium nitrate