RESUMO
Mixtures of [{PCy2(o-biphenyl)}AuCl] and AgSbF6 catalyze the tandem cycloaddition/hydroarylation of 7-aryl-1,6-enynes with electron-rich arenes to form 6,6-diarylbicyclo[3.2.0]heptanes in good yield under mild conditions. Experimental observations point to a mechanism involving gold-catalyzed cycloaddition followed by silver-catalyzed hydroarylation of a bicyclo[3.2.0]hept-1(7)-ene intermediate.
RESUMO
The cationic gold phosphine complex [{PCy2 (o-biphenyl)}Au(NCMe)](+) SbF6 (-) (Cy=cyclohexyl) catalyzes the intermolecular, anti-Markovnikov hydroamination reaction of monosubstituted and cis- and trans-disubstituted alkylidenecyclopropanes (ACPs) with imidazolidin-2-ones and other nucleophiles. This reaction forms 1-cyclopropyl alkylamine derivatives in high yield and with high regio- and diastereoselectivity. NMR spectroscopic analysis of gold π-ACP complexes and control experiments point to the spâ hybridization of the ACP internal alkene carbon atom as controlling the regiochemistry of the ACP hydroamination reaction.
RESUMO
The first asymmetric total synthesis of the marine natural product apratoxin D, a highly potent inhibitor of H-460 human lung cancer cell growth (IC(50) value of 2.6 nM), is described. Asymmetric N-amino cyclic carbamate (ACC) α,α-bisalkylation was utilized to establish the isolated C-37 methyl group with excellent selectivity. Other key asymmetric transformations employed were an Evans syn-aldol and a Paterson anti-aldol, both of which also proceeded with excellent stereoselectivity.
