Palladium-catalyzed seven-membered N,O-heterocycle ring formation

Bocelli, Gabriele; Catellani, Marta; Chiusoli, Gian Paolo; Cugini, Federica; Lasagni, Barbara; Mad, Matteo Neri

doi:10.1016/s0020-1693(97)05832-5

Cited by 11 publications

(9 citation statements)

References 39 publications

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“…Instead, and consistent with previous observation,2c weak support of the alkali metal is provided by the zincated aromatic carbon atom [2.600(8) Å]. We are not aware of any structural data in the literature on ortho ‐deprotonated aryl carbamates, though oxidative addition has afforded the bis(PPh 3 ) solvate of ortho ‐metalated ArPdI {Ar = C 6 H 4 [OC(O)N(Me)(CH 2 CH=CH 2 )]} 13…”

Section: Methodssupporting

confidence: 89%

Suppressing the Anionic Fries Rearrangement of Aryl Dialkylcarbamates; the Isolation of a Crystalline ortho‐Deprotonated Carbamate

et al. 2008

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In the presence of organolithium bases phenyl dialkylcarbamates have previously been shown to undergo facile rearrangement to yield the corresponding salicylamides. However, heterometallic lithium diethyl(2,2,6,6-tetramethylpiperidido)zincate achieves the clean directed ortho-metallation (DoM) of phenyl dialkylcarbamates, with [C 6 H 4 {OC(O)-Strategies aimed at achieving directed ortho-metalation (DoM) have been developed over a number of years, [1] and now represent a core tool in the elaboration of complex aromatic compounds. While organolithium reagents have historically been used to achieve this chemistry, their nucleophilicity has brought with it the risk of competing reactions at the directing group. The need to circumvent this issue has led to the design of the heterometallic bases R 2 Zn(TMP)Li [R = Et, tBu (1); TMP = 2,2,6,6-tetramethylpiperidide]. These have been successfully used to elaborate functionalised aromatic compounds incorporating directing groups normally susceptible to nucleophilic degradation. [2] Moreover, initial questions over whether these bases effect alkyl or amido basicity [3] appear to have now been resolved, with recent density functional theory (DFT) work establishing the view that they exhibit a kinetic preference for amido ligand exchange [4] according to a stepwise reaction mechanism.[4c] We have also used this idea to explain the experimentally observed polybasicity of 1 (R = Et, tBu). [4c,5] [a] Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K. NMe 2 }{Zn(µ-TMP)Et}Li] 2 having been structurally characterized. DFT studies point to a stepwise deprotonative mechanism in which the zincate reagent exhibits kinetic amido basicity.

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Section: Methodssupporting

confidence: 89%

Suppressing the Anionic Fries Rearrangement of Aryl Dialkylcarbamates; the Isolation of a Crystalline ortho‐Deprotonated Carbamate

et al. 2008

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“…It is presumably derived from the product of oxidative addition of 2amino-6-bromopyridine to bis(triphenylphosphine)palladium(0), followed by exchange of bromide for iodide, originating from the zinc reagent. Similar products have been obtained by other researchers in related reactions (Spee et al, 2000;Bocelli et al, 1998).…”

Section: Sup-1supporting

confidence: 89%

trans-(6-Amino-2-pyridinio)iodobis(triphenylphosphine)palladium(II) iodide ethyl acetate solvate

Clegg

Horsburgh

2003

Acta Cryst E

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The title compound, [Pd(C 5 H 6 N 2){(C 6 H 5) 3 P} 2 ]IÁC 4 H 8 O 2 , has a square-planar geometry for Pd, coordinated by two transphosphines, an iodo, and an aminopyridyl ligand. The cation, anion and solvent molecule all lie on a crystallographic mirror plane, and are connected together by NÐHÁ Á ÁI and NÐ HÁ Á ÁO hydrogen bonds. Comment The title compound, (I), was obtained unexpectedly as a byproduct in a reaction exploring the synthesis of enantiomerically pure pyridylamino acids via palladiumcatalysed cross-coupling of serine-derived organozinc reagents with various halopyridines (Tabanella et al., 2003). It is presumably derived from the product of oxidative addition of 2-amino-6-bromopyridine to bis(triphenylphosphine)palladium(0), followed by exchange of bromide for iodide, originating from the zinc reagent. Similar products have been obtained by other researchers in related reactions (Spee et al., 2000; Bocelli et al., 1998).

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“…On the basis of a search of the Cambridge Structural Database, it would appear that 6 represents the first example of a crystallographically characterized monomeric ortho -zincated (or indeed ortho -metalated) phenyl dialkyl O- carbamate to be prepared by direct metalation . Consequently, the aforementioned dimer 5 denotes the best comparison for compound 6 and emphasizes the effect of increased sterics on the constitution of the resulting structure.…”

Section: Resultsmentioning

confidence: 99%

Concerning the Structures of Alkali-Metal-MediatedorthoZincation of Benzamides and PhenylO-Carbamate

et al. 2010

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As a further contribution to alkali-metal-mediated metalation, a method for converting C−H bonds directly to C−Zn bonds without the need for an additional salt metathesis step, reactions of the sodium TMP-zincate [(TMEDA)Na(μ-TMP)(μ- t Bu)Zn( t Bu)] (1) with three different electron-rich aromatic substrates, have been investigated. Under ambient-temperature conditions, N,N-diethylbenzamide, N,N-diethyl-3-methoxybenzamide, and N,N-diethyl phenyl O-carbamate were zincated ortho to the substituent group (in between both substituents in the second case) in the crystalline products [(TMEDA)Na(μ-TMP){μ-2-[1-C(O)NEt2]C6H4}Zn( t Bu)] (3), [(TMEDA)Na(μ-TMP){μ-2-(1-C(O)NEt2)(3-OMe)C6H3}Zn( t Bu)] (4), and [(TMEDA)Na(μ-TMP){μ-2-(1-OC(O)NEt2)C6H4}Zn( t Bu)] (6). X-ray crystallography established that, in each case, the deprotonated aromatic fragment is captured by the residue of the bimetallic base, giving rise to seven-membered (NaNZnCCCO) ring structures for 3 and 4 and an eight-membered (NaNZnCCOCO) ring structure for 6. The new zincated aromatics were also characterized by solution-state 1H and 13C NMR spectroscopy. Reactivity studies of 3, 4, and 6 were also performed with iodine. In each case, three molar equivalents of iodine in THF solution gave the ortho-iodo products N,N-diethyl-2-iodobenzamide (7), N,N-diethyl-2-iodo-3-methoxybenzamide (8), and N,N-diethyl-2-iodophenyl-O-carbamate (9) in quantitative, 71% and 75% yields as determined by NMR analysis, respectively.

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Palladium-catalyzed seven-membered N,O-heterocycle ring formation

Cited by 11 publications

References 39 publications

Suppressing the Anionic Fries Rearrangement of Aryl Dialkylcarbamates; the Isolation of a Crystalline ortho‐Deprotonated Carbamate

Suppressing the Anionic Fries Rearrangement of Aryl Dialkylcarbamates; the Isolation of a Crystalline ortho‐Deprotonated Carbamate

trans-(6-Amino-2-pyridinio)iodobis(triphenylphosphine)palladium(II) iodide ethyl acetate solvate

Concerning the Structures of Alkali-Metal-MediatedorthoZincation of Benzamides and PhenylO-Carbamate

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