- Cyclopalladation and reactivity of amino esters through C - H bond activation: Experimental, kinetic, and density functional theory mechanistic studies
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The orthopalladation, through C - H bond activation, of a large number of amino esters and amino phosphonates derived from phenylglycine, and having different substituents at the aryl ring and the C-α atom, as well as on the N-amine atom, has been studied. The experimental observations indicated an improvement in the yields of the orthopalladated compounds when the N-amine and/or the C-α atom are substituted, when compared with the unsubstituted methyl phenylglycinate derivatives. In contrast, substitutions at the aryl ring do not promote significant changes in the orthometalation results. Furthermore, the use of hydrochloride salts of the amino esters has also been shown to have a remarkably favorable effect on the process. All these observations have been fully quantified at different temperatures and pressures by a detailed kinetic study in solution in different solvents and in the presence and absence of added Bronsted acids and chloride anions. The data collected indicate relevant changes in the process depending on these conditions, as expected from the general background known for cyclopalladation reactions. An electronic mechanism of the orthopalladation has been proposed based on DFT calculations at the B3LYP level, and a very good agreement between the trends kinetically measured and the theoretically calculated activation barriers has been obtained. The reactivity of the new orthopalladated amino phosphonate derivatives has been tested and it was found that their halogenation, alkoxylation and carbonylation resulted in formation of the corresponding functionalized ortho- haloaminophosphonates, ortho-alkoxyaminophosphonates and oxoisoindolinylphosphonates. Remote control: The orthopalladation, through C - H bond activation, of substituted amino esters and amino phosphonates derived from phenylglycine has been studied (see scheme). Determination of the reaction rates indicated a clear acceleration of the C - H activation rate when the n-amine and/or the C-α atom are substituted. Substitutions at the aryl ring do not promote changes. The use of hydrochloride salts of the amino esters also has a strong accelerating effect on the process.
- Laga, Eduardo,Garcia-Montero, Angel,Sayago, Francisco J.,Soler, Tatiana,Moncho, Salvador,Cativiela, Carlos,Martinez, Manuel,Urriolabeitia, Esteban P.
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p. 17398 - 17412
(2014/01/06)
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- The reaction of optically active α-aminocarboxylic acid hydrazides with triethyl orthoesters
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New derivatives of 2-(1-amino-1-phenylmethyl)-1,3,4-oxadiazole and 1,2,4-triazin-6-one were synthesised in the reactions of optically active α-aminocarboxylic acid hydrazides and triethyl orthoesters in xylene. The electronic and steric effects of substituents at the α position influencing the formation of five- or six-membered products are discussed.
- Kudelko, Agnieszka,Zieliński, Wojciech,Ejsmont, Krzysztof
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experimental part
p. 7838 - 7845
(2011/10/12)
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