Rate enhancing ligands for lead(IV)-mediated arylations

Buston, Jonathan Ε. H.; Moloney, Mark G.; Parry, Abigail V. L.; Wood, Paul T.

doi:10.1016/s0040-4039(02)00510-5

Cited by 17 publications

(13 citation statements)

References 13 publications

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“… 14 The failure of these methods prompted us to examine the α-arylation of β-ketoesters using an aryllead as the electrophilic reagent. Although the use of these complexes is well-established, 11 there are no examples of using an aryl azide substituent (much less an o -azide) in the α- arylation processes. The requisite 2-azidoaryllead acetate was readily prepared from either the 2-azidoarylboronic acid pinacolate ester ( 8 ) 15 or analogous stannane using the conditions reported by Pinhey and co-workers without any decomposition of the azido group.…”

mentioning

confidence: 99%

Efficient Synthesis of 3H-Indoles Enabled by the Lead-Mediated α-Arylation of β-Ketoesters or γ-Lactams Using Aryl Azides

Zhou

Driver

2014

Org. Lett.

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The development of a lead-mediated α-arylation reaction between aryl azides and β-ketoesters or γ-lactams that facilitates the formation of 3H-indoles is disclosed. Twenty-five examples are included which demonstrate the generality of this reaction to access aryl azides bearing tetrasubstituted o-alkyl substituents. When paired with a Staudinger reduction, this reaction streamlines the synthesis of functionalized 3H-indoles.

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mentioning

confidence: 99%

Efficient Synthesis of 3H-Indoles Enabled by the Lead-Mediated α-Arylation of β-Ketoesters or γ-Lactams Using Aryl Azides

Zhou

Driver

2014

Org. Lett.

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“…In the case of organolead-mediated C-arylation reactions, it was suggested that pyridine acts as a ligand donor rather than as a base. 24 Moreover, Moloney's results 25 as well as our recent studies 13 showed that the nature of the base (or additive) can strongly affect the yields and kinetics of the organolead-mediated reductive coupling reactions. However, the origin of these effects remains unclear.…”

Section: Methodsmentioning

confidence: 88%

Polyfunctionalized Aryllead Triacetates in a Cascade Synthesis of Tetracyclic Isochromanocoumarin-Type Compounds

Naumov¹,

Ganina²,

Shavirin³

et al. 2005

Synthesis

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“…The supernatant liquid was then decanted and the crystals washed with cold hexane under an argon atmosphere and dried in vacuo, to yield the lead(IV) tetraacetate-pyridine (LTA-py) complex (1.49 g, 72%). Elemental analysis: C, 28 …”

Section: Experimental Preparation Of the Complexmentioning

confidence: 99%

“…However, indirect evidence for its role as a ligand has come from recent observations that pyridine catalyses ligand redistribution between aryllead triacetates and diaryllead diacetates, 27 and that it, along with other sp 2 -hybridized amines, effectively catalyzes lead(IV) mediated arylation reactions. 28 That this coordinative effect could be put to valuable synthetic effect was recently indicated by Yamamoto and co-workers, 22 who showed that useful enantiocontrol and conversion yields could be achieved in biaryl coupling reactions mediated by lead(IV) in the presence of chiral amines (e.g. brucine) although incorporation of such r-donors within a ligand neither enhanced yields nor enantioselectivity in arylation reactions.…”

Section: Introductionmentioning

confidence: 99%

Structural investigations of a lead(iv) tetraacetate–pyridine complex

et al. 2005

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A 1 : 1 crystalline complex of lead(IV) tetraacetate and pyridine (LTA-py) has been prepared. The single-crystal X-ray structure, at 296 and 150 K, establishes the presence of a relatively short Pb-N bond (2.307 A) within an intriguing seven-coordinate lead inner sphere consisting of the pyridine ligand and two bidentate and two monodentate acetate ligands. The pyridine occupies a surprising amount of the available coordination space and has induced a dramatic change in coordination compared to the four chelating acetate ligands found in lead tetraacetate (LTA). Thermal measurements (TGA/DSC) indicate the de-coordination of pyridine and its loss from the solid between 360 and 380 K. (207)Pb CP/MAS NMR spectroscopy also demonstrates the existence of the Pb-N bond through observation of (1)J((207)Pb,(14)N)= 63 Hz and a (207)Pb-(14)N dipolar coupling constant, of 149 Hz. The solid-state (207)Pb NMR parameters are used to give insight into the coordination environment of Pb(iv) in LTA-py. In solution, ligand exchange is rapid on chemical shift and J-coupling time scales. A (207)Pb NMR study of the titration of an LTA solution by pyridine yields a stability constant for LTA-py of K = 1.5 M(-1) and predicts it to have a (207)Pb NMR chemical shift essentially identical to that observed by CP/MAS NMR in the solid state. This correlation between the solid state and solution indicates that the seven-coordinate LTA-py structure found in the crystalline state does persist in solution, and this could further explain why the addition of pyridine has such profound effects on lead(IV) carboxylate-mediated organic reactions. Simulations of exchange-broadened line shapes of (13)C CP/MAS NMR spectra in the temperature regime above 280 K indicate local motion of the pyridine rings in the form of 180 degrees jumps (activation energy 72.5 kJ mol(-1)); these are first such ring flips reported for a coordinated pyridine ligand.

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Rate enhancing ligands for lead(IV)-mediated arylations

Cited by 17 publications

References 13 publications

Efficient Synthesis of 3H-Indoles Enabled by the Lead-Mediated α-Arylation of β-Ketoesters or γ-Lactams Using Aryl Azides

Efficient Synthesis of 3H-Indoles Enabled by the Lead-Mediated α-Arylation of β-Ketoesters or γ-Lactams Using Aryl Azides

Polyfunctionalized Aryllead Triacetates in a Cascade Synthesis of Tetracyclic Isochromanocoumarin-Type Compounds

Structural investigations of a lead(iv) tetraacetate–pyridine complex

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