Efficient synthesis of enantiomerically pure alpha-alkyl cyclopropanecarbonitrile derivatives from pyrazolines.
[reaction: see text] Thermolysis of enantiopure sulfonyl pyrazolines 4 and 5, easily obtained from (Z)-3-p-tolylsulfinylacrylonitriles (1), afforded sulfonyl cyclopropanes (6, 7) in a completely stereoselective manner in almost quantitative yields. Both cyclopropanes and alkylidenecyclopropanes, containing one or two chiral carbon atoms, one of them being quaternary, were obtained by hydrogenolysis of the C-S bonding and under the conditions reported by Julia, respectively. The highly stereoselective extrusion of nitrogen suggests a concerted mechanism.
García Ruano
José L
JL
Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain. joseluis.garcia.ruano@uam.es
Alonso de Diego
Sergio A
SA
Martín
M Rosario
MR
Torrente
Esther
E
Martín Castro
Ana M
AM
D003521:Cyclopropanes / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D009570:Nitriles / Q000138:chemical synthesis* / Q000737:chemistry; D011720:Pyrazoles / Q000737:chemistry*; D013237:Stereoisomerism
D003521:Cyclopropanes; D009570:Nitriles; D011720:Pyrazoles; C510307:cyclopropanecarbonitrile