Synthesis and characterization in solution and in the solid State of the palladium aryl bromide complexes [Pd(Ar)Br{(S)-BINAP}]: formation of cyclopalladated complexes and direct observation of a C-N reductive elimination to form heterocycles

Monteiro, Adriano L.; Davis, W. M.

doi:10.1590/s0103-50532004000100014

Cited by 12 publications

(13 citation statements)

References 13 publications

(26 reference statements)

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“…4 ). The Pd–Br distance is calculated to be 2.60 Å and is consistent with similar Pd–Br bond lengths found in the literature for single crystal X-ray structures [ 47 – 48 ]. This oxidative addition step involves a low activation energy barrier of −43.9 kcal/mol.…”

Section: Resultssupporting

confidence: 88%

“…The reaction then proceeds via transition state TS2 , leading to the cleavage of the C(sp 2 )–Br bond and the formation of a new Pd–C(sp 2 ) bond, to form a cis intermediate of energy −93.0 kcal/mol. The new Pd–C(sp 2 ) bond distance of 2.00 Å falls within the reported Pd–C(sp 2 ) bond distances [ 47 – 48 ]. Since the bromo ligand is larger in atomic radius than the chloro ligands the more stable form of the oxidative addition product is the trans form.…”

Section: Resultssupporting

confidence: 86%

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Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

Fiebor

Tia

Makhubela

et al. 2018

Beilstein J. Org. Chem.

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Unlike their SCS analogues, SNS pincer complexes are poorly studied for their use in coupling reactions. Accordingly, a series of water soluble cationic Pd(II) SNS pincer complexes have been successfully synthesised and investigated in detail for their catalytic activity in Suzuki–Miyaura coupling reactions. By using only 0.5 mol % loading of the complexes, the coupling of inactivated aryl bromides and activated aryl chlorides with various boronic acids in water was achieved in excellent yields and the catalysts were found to be reusable for three cycles without a significant loss of activity. The investigation of the mechanism of the reaction revealed that a Pd(II) to Pd(IV) route is the more likely pathway which was further supported by computational studies.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 86%

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

Fiebor

Tia

Makhubela

et al. 2018

Beilstein J. Org. Chem.

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“…Their solid-state IR spectra show the ν(CO) band at 1551 (3a) or 1558 (3b) cm −1 , which is typical of N-coordinated amidato complexes. 32,33 The attempts to deprotonate the α-CH 2 in the NMe 2 derivative 1c with KO t Bu were unsuccessful.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The coordination environment and bond distances and angles around the Pd center are similar to those found in analogous derivatives. 30,33,36,54 Molecules are linked via hydrogen bonds N−H•••I to form zigzag chains parallel to the c axis.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis and Reactivity of Ortho-Palladated 3-Phenylpropanamides. Insertion of CO, XyNC, and Alkynes into the Pd–C Bond. Synthesis of Seven- and Nine-Membered Palladacycles and Benzazepine- and Benzazonine-Based Heterocycles

et al. 2013

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Aryl palladium complexes [Pd{C 6 H 4 (CH 2 ) 2 C(O)-NRR′)-2}I(tmeda)] [NRR′ = NH 2 (1a), NHMe (1b), NMe 2 (1c); tmeda = N,N,N′,N′-tetramethylethylenediamine] are prepared by oxidative addition of the corresponding 3-(2iodophenyl)propanamides to "Pd(dba) 2 " ([Pd 2 (dba) 3 ]•dba; dba = dibenzylideneacetone) in the presence of tmeda. The cationic seven-membered palladacycles [Pd{κ 2 C,O-C 6 H 4 (CH 2 ) 2 C(O)-NRR′)-2}(tmeda)]TfO (2a−c) are obtained by reacting 1a−c with AgTfO. Neutral amidate complexes of the type [Pd{κ 2 C,N-C 6 H 4 (CH 2 ) 2 C(O)NR)-2}(tmeda)] [R = H (3a), Me (3b)] are obtained upon deprotonation of the amide function in 1a or 1b with KO t Bu. The reaction of 1a with CO at room temperature affords the stable acyl derivative [Pd{C(O)C 6 H 4 (CH 2 ) 2 C-(O)NH 2 -2}I(tmeda)] (4), while 2a gives Pd, (tmedaH)TfO, and 4,5-dihydro-2H-benzo[c]azepine-1,3-dione (5a). Compound 5a can also be obtained in high yield by treating the amidate complex 3a with CO, while a low yield of 2-methyl-4,5-dihydro-2Hbenzo[c]azepine-1,3-dione (5b) was obtained from 3b under the same conditions. Complexes 1a−c react with 3 equiv of XyNC to give trans-[Pd{C(NXy)C 6 H 4 (CH 2 ) 2 C(O)NRR′-2}I(CNXy) 2 ] [NRR′ = NH 2 (6a), NHMe (6b), NMe 2 (6c)]. By refluxing a CHCl 3 solution of 6a or 1a and XyNC in 1:1 molar ratio, mixtures of 1-(2,6-dimethylphenylimino)-1,2,4,5tetrahydrobenzo[c]azepin-3-one (7a) and 2-(2-cyanoethyl)-N-(2,6-dimethylphenyl)benzamide (8a) are obtained. Complexes 2a−c react with alkynes in 1:1 molar ratio to give nine-membered palladacycles of the type [Pd{κ 2 C,O-C(X) C(X)C 6 H 4 (CH 2 ) 2 C(O)NRR′-2}(tmeda)]TfO [NRR′ = NH 2 , X = Ph (9a), C 6 H 4 n Bu-4 (10a), C 6 H 4 Br-4 (11a), CO 2 Me (12a); NRR′ = NHMe, X = Ph (9b); NRR′ = NMe 2 , X = Ph (9c)]. The reaction of 2a with an excess of 3-hexyne gives the complex [Pd{η 3 -C 6 H 4 (C 4 Et 4 )(CH 2 ) 2 C(O)NH 2 }(tmeda)]TfO (13), containing a spirocyclic ligand coordinated to Pd through a η 3 -allylic bond. The derivatives 9a, 10a and 11a react with CO at 50 °C in CHCl 3 to give colloidal Pd, (tmedaH)TfO, and the corresponding 6,7-disubstituted 1,2-dihydro-4H-benzo[e]azonine-3,5-diones (14, 15, 16), which result from a CO insertion/C− N reductive coupling sequence.

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“…Alternativamente, a ressonância magnética nuclear (RMN) pode ser também empregada na caracterização de uma relação atropoisomérica em compostos diastereoisoméricos, que já apresentam um centro estereogênico ou mais que um eixo de quiralidade [18][19][20][21][22] . Podese observar, em estudos de dinâmica molecular de derivados de 1,8-bispiridil-naftalenos descritos por Wolf e Ghebremariam 16 , que sinais referentes aos grupos metila do derivado 20 apresentavam diferenciação entre os atropoisômeros diastereoisoméricos sin e anti, à medida que a temperatura de análise era reduzida (Figura 8).…”

Section: Métodos De Determinação E Resolução De Atropoisômerosunclassified

Atropoisomerismo: o efeito da quiralidade axial em substâncias bioativas

Santos¹,

Pinheiro²,

Sodero³

et al. 2007

Quím. Nova

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Recebido em 26/9/05; aceito em 30/3/06; publicado na web em 26/9/06 ATROPISOMERISM: THE EFFECT OF THE AXIAL CHIRALITY IN BIOACTIVE COMPOUNDS. Atropisomerism is a special kind of stereoisomeric relationship that arises from the freezing of a certain conformation of an organic molecule, associated with a high rotational barrier about a single covalent bond. Atropisomerism has been originally described in orto-functionalyzed biphenyl derivatives, but a lot of other organic functionalities can present this structural phenomenon, characterized by the presence of chiral properties in compounds that don't present classical stereogenic centers. Atropisomeric compounds, intermediates and catalysts have well-know importance in organic synthesis, but the influence of the axial chirality in substances able to modulate biological systems is still not very exploited in drug design and development. In this context, the present account describes the importance of this structural property in the medicinal chemistry of different classes of bioactive compounds or therapeutic agents, emphasizing how atropisomerism could affect the molecular recognition of a ligand or a prototype by the target bioreceptor.Keywords: atropisomerism; atropisomerism of drugs; stereoselective molecular recognition. INTRODUÇÃOO fenômeno conhecido como atropoisomerismo, denominação oriunda da palavra grega atropos (i.e. sem rotação), é atribuído a um tipo de estereoisomerismo característico de sistemas onde a rotação livre em torno de uma ligação simples é impedida, produzindo uma barreira energética suficientemente elevada, de modo a permitir o isolamento ou simplesmente a detecção dos diferentes rotâmeros, chamados atropoisômeros 1,2 . Este tipo de isomeria axial é caracterizada pela atividade ótica promovida por um eixo de ligação, não necessitando que a substância apresente carbono estereogênico como elemento de quiralidade. O fenômeno foi observado pela primeira vez por Christie e Kenner 3 , após a resolução dos atropoisômeros do ácido 6,6'-dinitro-2,2'-difênico 1, os quais não se mostraram interconversíveis à temperatura ambiente (Figura 1).A nomenclatura de substâncias que apresentam quiralidade axial pode ser atribuída como R ou S pela aplicação das regras de prioridade de Cahn-Ingold-Prelog 4,5 , conforme exemplificado na Figura 2. A partir da projeção da estrutura vista na direção do eixo de ligação do sistema bifenílico, deve-se definir a ordem de prioridade dos grupos funcionais, iniciando por aqueles mais próximos ao observador e, em seguida, atribuir a configuração absoluta R ou S com base no sentido da rotação produzida quando se caminha do substituinte de maior prioridade para o de menor prioridade. Apesar de ser opcional, a descrição da configuração absoluta de estereoisômeros atropoisoméricos deve ser acompanhada pela introdução do prefixo a, i.e. aR ou aS, visando distinguí-los de outros tipos de compostos oticamente ativos. De maneira alternativa, os compostos atropoisoméricos podem ser vistos como hélices e suas configurações descritas...

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Synthesis and characterization in solution and in the solid State of the palladium aryl bromide complexes [Pd(Ar)Br{(S)-BINAP}]: formation of cyclopalladated complexes and direct observation of a C-N reductive elimination to form heterocycles

Abstract: As reações de uma mistura [Pd 2 (dba) 3 ]/P(o-tolyl) 3 (1/4) com brometos de arila orto substituídos conduziram aos dímeros [Pd(Ar)(µ-Br){P(o-tolyl) 3 )}] 2 que, após adição de 2 equiv. de (S)-BINAP formaram os complexos ){(S)-BINAP}] em bons rendimentos (57-89%

Cited by 12 publications

References 13 publications

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

Synthesis and Reactivity of Ortho-Palladated 3-Phenylpropanamides. Insertion of CO, XyNC, and Alkynes into the Pd–C Bond. Synthesis of Seven- and Nine-Membered Palladacycles and Benzazepine- and Benzazonine-Based Heterocycles

Atropoisomerismo: o efeito da quiralidade axial em substâncias bioativas

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