KO<i>t</i>Bu‐Catalyzed Michael Addition Reactions Under Mild and Solvent‐Free Conditions

Thiyagarajan, S.; Krishnakumar, Varadhan; Gunanathan, Chidambaram

doi:10.1002/asia.201901647

Cited by 37 publications

(16 citation statements)

References 50 publications

(99 reference statements)

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“…As another example, our group described that a copper catalyst could control the selectivity of the aza‐Michael addition of indole to vinyl sulfones, providing the desired β ‐indole‐substituted sulfones in high efficiencies [10] . During our studies, Gunanathan and co‐workers reported that KO t ‐Bu could selectively catalyze the conjugate addition of azoles, including an indole, to α , β ‐unsaturated nitriles under mild reaction conditions [11] . Although these reported reactions are highly regio‐ and chemoselective, a number of drawbacks should be addressed to improve their synthetic utility.…”

Section: Introductionmentioning

confidence: 92%

KOt‐Bu‐Catalyzed Chemo‐ and Regioselective Hydroamination of Allylic Sulfones with Indoles

2020

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A highly chemo‐ and regioselective KOt‐Bu‐catalyzed addition of substituted indoles to terminal or disubstituted allylic sulfones at the indole N‐position is reported. The catalytic protocol allows for the efficient and mild synthesis of a broad range of new and versatile sulfonyl‐substituted indoles and azoles bearing various functional groups from readily available starting materials in good to excellent yields with complete regioselectivity.

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Section: Introductionmentioning

confidence: 92%

KOt‐Bu‐Catalyzed Chemo‐ and Regioselective Hydroamination of Allylic Sulfones with Indoles

2020

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“…For example, addition product 1c has been obtained in 93% conversion before using 10 mol % TPP, 3 equiv c and heating the reaction mixture for 8 h under refluxing conditions [14]. However, with base catalysis (KOt-Bu) even better results than those presented here can be achieved [22,23].…”

Section: Resultsmentioning

confidence: 67%

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Fischer¹,

Renner²,

Boese³

et al. 2021

Beilstein J. Org. Chem.

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Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine–Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa-Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80 °C resulted in macromolecules containing a considerable share of Rauhut–Currier-type repeat units and consequently lower molar masses were obtained.

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“…Products 36 and 27 are transformed to the corresponding lactone products 92 and 93 in 80%, and 66% yields, respectively (Scheme c(i),(ii)). In addition, δ-hydroxynitriles 25 and 21 underwent the Michael addition reaction to provide products 94 and 95 in very good yields (Scheme c(iii),(iv)) …”

Section: Resultsmentioning

confidence: 99%

Catalytic Formal Conjugate Addition: Direct Synthesis of δ-Hydroxynitriles from Nitriles and Allylic Alcohols

et al. 2022

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Alcohols and nitrile functionalities have widespread applications in biochemical and chemical synthesis. Catalytic transformations involving C−C bond formation relying on unsaturated coupling partners create important pathways for processes in synthetic, material, and medicinal chemistry. The discovery of a simple and selective coupling of nitriles with allylic alcohols catalyzed by a ruthenium pincer complex is described, which tolerates reactive functional groups such as carbamate, sulfonate, olefin, cyano, and trifluoromethyl-substituted benzyl nitriles. Homo allylic alcohols also provided 1,4-addition products following the isomerization of double bonds. Mechanistic studies supported that the allylic alcohols initially undergo selective oxidation by the catalyst to α,β-unsaturated carbonyl compounds followed by 1,4-conjugate addition of benzyl nitriles catalyzed by a base and subsequent catalytic reduction of carbonyl functionality, leading to the formation of δ-hydroxynitrile products. The catalytic cycle of this tandem process is established by density functional theory studies. Remarkably, anipamil drug is successfully synthesized using this catalytic protocol. The utility of the δ-hydroxynitrile products in the synthesis of biologically active molecules and their further functionalization are also demonstrated.

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KOtBu‐Catalyzed Michael Addition Reactions Under Mild and Solvent‐Free Conditions

Cited by 37 publications

References 50 publications

KOt‐Bu‐Catalyzed Chemo‐ and Regioselective Hydroamination of Allylic Sulfones with Indoles

KOt‐Bu‐Catalyzed Chemo‐ and Regioselective Hydroamination of Allylic Sulfones with Indoles

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Catalytic Formal Conjugate Addition: Direct Synthesis of δ-Hydroxynitriles from Nitriles and Allylic Alcohols

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