"Umpolung" Using a Phosphorus Group. A Novel Method for the Chemoselective Synthesis of 2-Acetonyl or 3-Acetonyl Morpholines

Cristau, Henri‐Jean; Fonte, Marie; Torreilles, E.

doi:10.1055/s-1989-27232

Cited by 12 publications

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“…Under phosphine catalysis, a distinctive mode of annulation, through a γ-umpolung–Michael reaction, can occur when reacting dipronucleophiles with activated allenes. Cristau, in 1989, was the first to realize this concept, albeit in a noncatalytic manner . Starting from the phosphonium iodide 79 , γ-umpolung addition occurred readily at the nitrogen center of 2-benylaminoethanol to furnish the intermediate 92 (Scheme ).…”

Section: Nucleophilic Phosphine Catalysis Of Allenesmentioning

confidence: 99%

“…While tertiary phosphine catalysts facilitate Michael additions of nucleophiles onto electron-deficient olefins, γ-umpolung reactions occur when electron-deficient allenes react with nucleophiles in the presence of a phosphine catalyst. Cristau, in 1982, was the first to exercise the concept of umpolung addition to activated allenes, but not under catalysis conditionsrather by treating the isolated vinyl phosphonium iodide 74 183,184 with lithium methoxide in methanol (Scheme 113). Taking 3,4-pentadienone (73) as their substrate of interest, triphenylphosphine underwent facile addition into the allenyl double bond.…”

Section: Phosphine-catalyzed Isomerization Of Allenes To Dienesmentioning

confidence: 99%

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Phosphine Organocatalysis

et al. 2018

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The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon–carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita–Baylis–Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material—nucleophiles, dinucleophiles, electrophiles, and electrophile–nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon–carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon–carbon multiple bond–containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide–generating reactions.

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Section: Nucleophilic Phosphine Catalysis Of Allenesmentioning

confidence: 99%

Section: Phosphine-catalyzed Isomerization Of Allenes To Dienesmentioning

confidence: 99%

Phosphine Organocatalysis

et al. 2018

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“…Double-Michael reactions of dinucleophiles with allenes, which have the same degree of unsaturation as acetylenes yet enhanced reactivity, would conceivably also yield heterocycles B ; 10 it has been reported, however, that allenes typically undergo tandem γ-umpolung addition/Michael cyclization, forming heterocycles C , in the presence of phosphines. 11 Herein, we report a new phosphine-triggered general base-catalyzed tandem double-Michael reaction of dinucleophiles with allenes, affording, under simple and mild conditions, highly functionalized heterocycles B featuring fully substituted carbon centers. …”

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confidence: 99%

“…11 Indeed, treatment of N -tosyl-2-aminophenol ( 1a ) 12 and the allene 2a with PPh 3 (10 mol %) provided the benzomorpholine 3a in 88% yield (Eq 2). Switching the catalyst to PMe 3 , however, led to production of the double-Michael product 4a in 92% yield.…”

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confidence: 99%

“…Protonation of 6 by the pronucleophile 1 leads to the formation of a nucleophile/phosphonium salt pair 7·8 , which undergoes γ-umpolung addition to yield the ylide 9 when PPh 3 is employed as the catalyst. 11 In contrast, the more-electron-rich phosphine PMe 3 does not facilitate umpolung addition. 22 As we had observed for the double-Michael reactions of acetylenes, the β,β-disubstituted enoate 10 did not undergo the Michael reaction.…”

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Phosphine-Initiated General Base Catalysis: Facile Access to Benzannulated 1,3-Diheteroatom Five-Membered Rings via Double-Michael Reactions of Allenes

2011

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General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excellent yields. Careful mechanistic studies unveiled the phosphine-triggered general base catalysis pathway. Furthermore, the double-Michael reaction can serve as an alternative method for the selective mono-ketalization of β-diketones.

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Phosphine‐Catalyzed (4+1) Annulation: Rearrangement of Allenylic Carbamates to 3‐Pyrrolines through Phosphonium Diene Intermediates

2020

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We have developed a phosphine‐catalyzed (4+1) annulative rearrangement for the preparation of 3‐pyrrolines from allenylic carbamates via phosphonium diene intermediates. We employed this methodology to synthesize an array of 1,3‐disubstituted‐ and 1,2,3‐trisubstituted‐3‐pyrrolines, including the often difficult to prepare 2‐alkyl variants. A mechanistic investigation employing allenylic acetates and mononucleophiles unexpectedly unveiled that a phosphine‐catalyzed (4+1) reaction for the construction of cyclopentene products, previously reported by Tong, might not occur through a phosphonium diene, as had been proposed, but rather through multiple mechanisms working in concert. Consequently, our phosphine‐catalyzed rearrangement is most likely the first transformation to involve the unequivocal formation of a phosphonium diene intermediate along the reaction pathway. To demonstrate the synthetic utility of this newly developed reaction, we have completed concise formal syntheses of the pyrrolizidine alkaloids (±)‐trachelanthamidine and (±)‐supinidine.

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"Umpolung" Using a Phosphorus Group. A Novel Method for the Chemoselective Synthesis of 2-Acetonyl or 3-Acetonyl Morpholines

Cited by 12 publications

References 0 publications

Phosphine Organocatalysis

Phosphine Organocatalysis

Phosphine-Initiated General Base Catalysis: Facile Access to Benzannulated 1,3-Diheteroatom Five-Membered Rings via Double-Michael Reactions of Allenes

Phosphine‐Catalyzed (4+1) Annulation: Rearrangement of Allenylic Carbamates to 3‐Pyrrolines through Phosphonium Diene Intermediates

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