An efficient rhodium‐catalyzed asymmetrichydrogenation of challenging tetrasubstituted cyclic enamides has been developed, affording cyclic chiral amides with high yields and excellent enantioselectivities (up to 99% yield and >99% ee). This novel methodology provides an efficient and concise synthetic route to chiral cycloalkylamines with two contiguous stereogenic centers. The potential utility
β- and γ-lactams by nickel powder mediated 4-exo or 5-endo radical cyclisations. A concise construction of the mesembrine skeleton
作者:Jérôme Cassayre、Béatrice Quiclet-Sire、Jean-Baptiste Saunier、Samir Z. Zard
DOI:10.1016/s0040-4020(97)10204-6
日期:1998.2
N-Alkenyl trichloroacetamides, upon treatment with nickelpowder and aceticacid in refluxing 2-propanol undergo reversible 4-exo radicalcyclisation. The cyclised radical can be trapped in different ways leading to β-lactams. When the trap is omitted or not efficient enough, unusual irreversible 5-endo cyclisation occurs affording functionalised five-membered lactams. Synthesis of bicyclic γ-lactams
Stereoselective Formal Synthesis of (-)-mesembrane via Asymmetric Allylation and Resoluting Condensation Reactions
作者:Ji-Hye Park、Young-Kwang Kim、Gun-Cheol Kim
DOI:10.5012/bkcs.2011.32.8.3141
日期:2011.8.20
C in the presence of TsOH. Among four chiral auxiliaries selected for the preparation of 7, two (Entry 1 and 2) provided 2:1 selectivity in 50 and 70% yields. Although the selectivity was moderate, we expected that this step would be helpful to increase the selectivity as an ancillary step and provide a known chiral intermediate. We have tried asymmetric allylation of allyl enolcarbonate 9 to find