154244-19-6Relevant academic research and scientific papers
82. Enantioselective reduction of electrophilic C=C bonds with sodium tetrahydroborate and 'semicorrin' cobalt catalysts
Misun, Marian,Pfaltz, Andreas
, p. 961 - 972 (2007/10/03)
'Semicorrin' cobalt complexes, prepared in situ from cobalt(II) chloride and the corresponding ligands, are efficient catalysts for the enantioselective reduction of electrophilic C=C bonds with NaBH4. The best selectivities (> 90% ee) are achieved with α,β-unsaturated carboxamides and carboxylates. Analogous α,β-unsaturated nitriles, sulfones, and phosphonates afford enantiomenc excesses of 50-70%. Interestingly, in the reduction of α,β-unsaturated sulfones, the highest enantioselectivities were obtained with unsymmetrical 'semicorrins', whereas in all other cases C2-symmetric 'semicorrins' proved to be superior.
Cyclization of Alkoxyiminyl Radicals onto Olefins: Formation of 2-Alkoxy-Δ1-pyrrolines, 4,5-Dihydrooxazoles and 5,6-Dihydro-4H-1,3-oxazines
Glover, Stephen A.,Hammond, Gerard P.,Harman, David G.,Mills, John G.,Rowbottom, Colleen A.
, p. 1213 - 1228 (2007/10/02)
Alkoxyiminyl radicals, generated by photolysis of N-bromo imidates, undergo exo-1,5 and exo-1,6 cyclization onto olefins on the O-alkyl side chain giving good yields of 4,5-dihydrooxazoles and 5,6-dihydro-4H-1,3-oxazines, respectively. exo-1,5 Cyclization onto an olefin on the iminyl side chain gives 2-alkoxy-Δ1-pyrrolines. 4,5-Dihydrooxazole formation is more favourable than cyclization to 2-alkoxy-Δ1-pyrrolines and both reactions are irreversible.These preferences are supported by MNDO molecular orbital calculations which predict that both processes are exotermic but cyclization onto the O-alkenyl side chain has a lower ΔH(excit.).
