A robust method for preparing (3S)-3-alkyl-3-phenyl-1,4-dioxane-2,5-diones was developed using an improved cyclocondensation reaction between (S)-α-alkylmandelic acids and 2-bromocarbonyl halides. Subtle differences in the reaction conditions, including separate additions of triethylamine, significantly increased the yield compared with Schollkopf's original method.
Highly Stereoselective Synthesis of α-Alkyl-α-Hydroxycarboxylic Acid Derivatives Catalyzed by a Dinuclear Zinc Complex
作者:Barry M. Trost、Keiichi Hirano
DOI:10.1002/anie.201201116
日期:2012.6.25
dinuclear zinc–ProPhenol catalyst enables highly enantioselective nitro‐Michael reactions with oxazol‐4(5H)‐ones as nucleophilic substrates (see scheme, Nap=2‐naphthyl). This work highlights the utility of the ProPhenol family of ligands. The modular nature of these ligands proved crucial in the optimization of reaction conditions to achieve excellent stereoselectivities.
Synthesis of Highly Enantioenriched 3,4-Dihydroquinolin-2-ones by 6-<i>Exo-trig</i> Radical Cyclizations of Axially Chiral α-Halo-<i>ortho</i>-alkenyl Anilides
作者:David B. Guthrie、Steven J. Geib、Dennis P. Curran
DOI:10.1021/ja9066282
日期:2009.10.28
Radicalcyclizations (Bu(3)SnH, Et(3)B/air, rt) of racemic alpha-halo-ortho-alkenyl anilides provide 3,4-dihydroquinolin-2-ones in high yield. Cyclizations of enantioenriched precursors occur in similarly high yields and with transfer of axialchirality to the new stereocenter of the products with exceptionally high fidelity (often >95%). Single and tandem cyclizations of alpha-halo-ortho-alkenyl anilides