Synthesis of Chiral γ-Lactams via in Situ Elimination/Iridium-Catalyzed Asymmetric Hydrogenation of Racemic γ-Hydroxy γ-Lactams
作者:Qianjia Yuan、Delong Liu、Wanbin Zhang
DOI:10.1021/acs.orglett.7b00651
日期:2017.4.7
Chiral γ-lactams have been synthesized in excellent yields and enantioselectivities (up to 99% yield and 96% ee) from easily accessible racemic γ-hydroxy γ-lactams via an iridium-phosphoramidite catalyzed asymmetric hydrogenation. The reaction was designed based on insight into the reaction mechanism demonstrated in previous work and can be carried out at a reduced catalyst loading of 0.1 mol % on
Azide ring-opening-ring-closure reactions and tele-substitutions in vicinal azidopyrazole-, pyrrole- and indolecarboxaldehydes
作者:Jan Becher、Per Lauge Joergensen、Krystian Pluta、Niels J. Krake、Birgitte Falt-Hansen
DOI:10.1021/jo00033a039
日期:1992.3
5-Chloro-1-methylpyrazole-4-carboxaldehydes 1 react with excess sodium azide in dimethyl sulfoxide to produce a mixture of 1-azidomethyl-4-cyanopyrazoles 2 and 4-cyano-5-hydroxy-1-methylpyrazoles 3. Application of this reaction to the corresponding 5-chloro-1-phenylpyrazole-4-carboxaldehydes 5 gave 4-cyano-5-hydroxy-1-phenyl-pyrazoles 7 as the sole products in high yields. Likewise, 2-aryl-5-chloro-1-methylpyrrole-3,4-dicarboxaldehydes 9 rearranged to 2-aryl-4-cyano-5-hydroxy-1-methylpyrrole-3-carboxaldehydes 10 in high yields. In the indole series, treatment of 1-aryl-2-chloroindole-3-carboxaldehydes 11 with NaN3 yielded a mixture of 1-aryl-3-cyano-2(3H)-indolones 13 and 1-aryl-5-azido-3-cyanoindoles 12, both products resulting from a ring-opening-ring-closure reaction with concomitant nucleophilic tele-substitution at the 5-position of the indole ring.