Chiral Squaramide-Catalyzed Michael/Alkylation Cascade Reaction for the Asymmetric Synthesis of Nitro-Spirocyclopropanes
作者:Bo-Liang Zhao、Da-Ming Du
DOI:10.1002/ejoc.201500533
日期:2015.8
diastereoselective and enantioselective cyclopropanation reaction has been developed by employing a Michael/alkylationcascadereaction between (E)-3-arylenechroman-4-one or (E)-2-arylideneindan-1-one derivatives and a bromonitroalkane with a chiral squaramide catalyst. This reaction constitutes a facile asymmetricsynthesis for nitro-spirocyclopropanes that have three adjacent stereogenic centers, including
spiroheterocycles are considered as emerging drug candidates, synthesis of spiroaziridines has not been well explored so far. Herein, we disclose an efficient I2/TBHP mediated diastereoselectivesynthesis of N-alkyl spiroaziridines from primary amines and easily accessible α,β-unsaturated ketones. The reaction is also compatible for the synthesis of 2-aroylaziridines.
primary phosphines. Phosphines 16 have been used as nucleophilic catalysts in model cyclization reactions. Unlike 2-phospha[3]-ferrocenophanes with stereogenic α-carbons, the planar chiral derivatives 16 proved to be suitable catalysts for these processes. Thus, for instance, phosphine 16c successfully promotes the enantioselective [3+2] annulations of allenes and enones into functionalized cyclopentenes
Catalytic enantioselective cascade Michael/cyclization reaction of 3-isothiocyanato oxindoles with exocyclic α,β-unsaturated ketones en route to 3,2′-pyrrolidinyl bispirooxindoles
作者:Satavisha Kayal、Santanu Mukherjee
DOI:10.1039/c6ob02187e
日期:——
Cascade Michael/cyclization reactions between 3-isothiocyanato oxindoles and exocyclic α,β-unsaturated ketones are shown to proceed efficiently in the presence of a quinine-derived tertiary amino-squaramide catalyst and furnish 3,2′-pyrrolidinyl bispirooxindoles containing two spiro-quaternary and three contiguous stereocenters as a single diastereomer with excellent enantioselectivities (up to 99 : 1
BF<sub>3</sub>·Et<sub>2</sub>O mediated one-step synthesis of N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines
作者:C. T. Fathimath Salfeena、K. T. Ashitha、B. S. Sasidhar
DOI:10.1039/c6ob02133f
日期:——
A simple and efficient one-pot synthesis of N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines by a BF3·Et2O mediated novel methodology, from easily available α,β-unsaturated ketones/arylidene ketones, phenyl acetylenes and substituted nitriles, has been described. This novel annulation provides quick access to complex polycyclic frameworks with an excellent substrate