- Transition-Metal-Free Multiple Functionalization of Piperidines to 4-Substituted and 3,4-Disubstituted 2-Piperidinones
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Remote and multiple functionalization of piperidines without the use of transition-metal catalysts and elaborate directing groups is one of the major challenges in organic synthesis. Herein is reported an unprecedented two-step protocol that enables the multiple functionalization of piperidines to either 4-substituted or trans-3,4-disubstituted 2-piperidones. First, by exploiting the duality of TEMPO reactivity, which under oxidative and thermal conditions fluctuates between cationic and persistent-radical form, a novel multiple C(sp3)-H oxidation of piperidines to α,β-unsaturated 2-piperidones was developed. Second, the intrinsic low reactivity of the unsaturated piperidones toward conjugated Grignard additions was overcome by using trimethylsilyl chloride (TMSCl) as Lewis acid. Subsequently, conjugated Grignard addition/electrophilic trapping protocol provided substituted 2-piperidone intermediates, some of which were then transformed into pharmaceutical alkaloids.
- Chamorro-Arenas, Delfino,Nolasco-Hernández, Alejandro A.,Fuentes, Lilia,Quintero, Leticia,Sartillo-Piscil, Fernando
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supporting information
p. 4671 - 4676
(2020/03/10)
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- Allyl-Nickel Catalysis Enables Carbonyl Dehydrogenation and Oxidative Cycloalkenylation of Ketones
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We herein disclose the first report of a first-row transition metal-catalyzed α,β-dehydrogenation of carbonyl compounds using allyl-nickel catalysis. This development overcomes several limitations of previously reported allyl-palladium-catalyzed oxidation, and is further leveraged for the development of an oxidative cycloalkenylation reaction that provides access to bicycloalkenones with fused, bridged, and spirocyclic ring systems using unactivated ketone and alkene precursors.
- Huang, David,Szewczyk, Suzanne M.,Zhang, Pengpeng,Newhouse, Timothy R.
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supporting information
p. 5669 - 5674
(2019/04/26)
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- A REGIOSELECTIVE DIELS-ALDER SYNTHESIS OF ELLIPTICINE
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The trimethylsilyl trifluoromethanesulfonate accelerated Diels-Alder reaction between 1,3-dimethyl-4-(phenylsulfonyl)-4H-furoindole (3) and 5,6-dihydropyridones (10) shows high regioselectivity, yielding carbazole 11 upon hydrolytic workup.Carbazole 11b has been successfully converted to the pyridocarbazole alkaloid ellipticine (1).
- Davis, Deborah A.,Gribble, Gordon W.
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p. 1081 - 1084
(2007/10/02)
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