Probing the "additive effect" in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones.
The effect of chirality and steric bulk of 2,5-disubstituted piperazines as additives in the conjugate addition of 2-nitropropane to cyclohexenone, catalyzed by l-proline, was investigated. Neither chirality nor steric bulk affects the enantioselectivity of addition, which gives 86-93% ee in the presence of achiral and chiral nonracemic 2,5-disubstituted piperazines. Proline hydroxamic acid is shown for the first time to be an effective organocatalyst in the same Michael reaction.
Hanessian
Stephen
S
Department of Chemistry, Université de Montréal, Canada. stephen.hanessian@umontreal.ca
Govindan
Subramaniyan
S
Warrier
Jayakumar S
JS
D000473:Alkanes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D006877:Hydroxamic Acids / Q000737:chemistry*; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism
D000473:Alkanes; D006877:Hydroxamic Acids; D009574:Nitro Compounds; D011392:Proline