159497-37-7Relevant articles and documents
Synthesis of the C(1)-C(13) Fragment of Leiodermatolide via Hydrogen-Mediated C-C Bond Formation
Roane, James,Wippich, Julian,Ramgren, Stephen D.,Krische, Michael J.
supporting information, p. 6634 - 6637 (2017/12/26)
The C(1)-C(13) fragment of the antimitotic marine macrolide leiodermatolide is prepared in seven steps via hydrogenative and transfer-hydrogenative reductive C-C couplings. A hydrogen-mediated reductive coupling of acetylene with a Roche-type aldehyde is used to construct C(7)-C(13). A 2-propanol-mediated reductive coupling of allyl acetate with (E)-2-methylbut-2-enal at a low loading of iridium (1 mol %) is used to construct C(1)-C(6), which is converted to an allylsilane using Oestereich's copper-catalyzed allylic substitution of Si-Zn reagents. The union of the C(1)-C(6) and C(7)-C(13) fragments is achieved via stereoselective Sakurai allylation.
First Enantioselective Catalyst for the Rearrangement of Allylic Imidates to Allylic Amides
Calter, Michael,Hollis, T. Keith,Overman, Larry E.,Ziller, Joseph,Zipp, G. Greg
, p. 1449 - 1456 (2007/10/03)
A series of Pd(II) complexes containing chiral diamine ligands were investigated as asymmetric catalysts for the rearrangement of allylic imidates to allyl amides. The best catalysts were cations obtained by dechlorination of dichloro[ (S)-2-(isoindolinylmethyl)-N-methylpyrrolidine]palladium-(II) (17) with silver salts in CH2Cl2. Catalyst 18 was studied thoroughly and shown by 1H NMR and X-ray crystallography analysis to be a C1 symmetric dimer (Figure 1). A series of related catalysts 22-27 having various counterions and anionic ligands were also prepared and studied as asymmetric catalysts for the rearrangement of allylic AT-(4-trifluorophenyl)benzimidate 29 to allylic benzamide 30 (eq 4). Rearrangement of 29 in CH2Cl2 (48 h at 40°C) in the presence of 5 mol % of 18 affords (-)-30 in 69% yield and 55% ee. Enantioselection is increased to 60% when an isomerically pure sample of 18 is employed. Chemical correlation of allylic benzamide 30 with (R)-norvaline established that (-)-30 has the R absolute configuration (Scheme 3). A cyclization-induced rearrangement mechanism (Scheme 1) requires that in the major pathway the imidate nitrogen attacks the re face of the olefin with Pd coordinated to the si face. These studies constitute the first report of asymmetric catalysis of the rearrangement of allylic imidates to allylic amides. However, significant hurdles remain to be overcome before the enantioselective rearrangement of allylic imidates becomes a practical route to enantioenriched nitrogen compounds.
