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Enantioselective assembly of functionalized carbocyclic spirooxindoles using an l-proline derived thiourea organocatalyst†
V. Pratap Reddy Gajulapalli,Poopathy Vinayagam,Venkitasamy Kesavan
RSC Advances Pub Date : 12/19/2014 00:00:00 , DOI:10.1039/C4RA13711F
Abstract

Sequential vinylogous Michael addition–cyclization reactions of vinyl malononitriles with isatylidene malononitrile were accomplished using L-proline derived bifunctional thiourea. Cyclohexylidine malononitrile afforded exclusively the single diastereomer with good to excellent enantioselectivity (up to 99% ee) for diverse oxindole spirocyclohexene derivatives. Tetralone derived α,α-dicyano alkene was also employed to access spirocyclic oxindole scaffolds with an excellent level of stereoselectivity (up to 99% ee).

Graphical abstract: Enantioselective assembly of functionalized carbocyclic spirooxindoles using an l-proline derived thiourea organocatalyst
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