A new method for the regioselective synthesis of β-enamino acid derivatives

Fustero, Santos; Diaz, M. Dolores; Carlón, Raquel Pérez

doi:10.1016/s0040-4039(00)61664-7

Cited by 9 publications

(4 citation statements)

References 21 publications

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“…In this context, we have recently reported two new different approaches to β-enamino acid derivatives. A simple route to masked β-dehydroamino acids ( 1 − 2 , R 1 = H, R 2 = alkyl or aryl, R 3 = or ≠ H) starting from 2-alkyl-2-oxazolines or 2-alkyl-2-thiazolines and nitriles was initially described (Chart ). , More recently, a mild two-step procedure to synthesize β-enamino esters by reaction of ketimines with 1,1‘-carbonyl diimidazole and subsequent addition of the corresponding alcohols was developed 1 …”

Section: Introductionmentioning

confidence: 99%

An Efficient and Simple Entry toN-Substituted β-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines

Fustero

Navarro²,

Díaz³

et al. 1996

J. Org. Chem.

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Reaction of azaenolates of 2-alkyl-oxa(thia)zolines 6 with imidoyl chlorides 7 as electrophiles to furnish masked N-substituted beta-enamino acid derivatives 1-2 in 70-90% yield is described. Alternative routes are discussed. Compounds 1-2 generally appear in one tautomeric form, imino or enamino, depending on the nature of the imidoyl chloride. The configuration of the enamino moiety (Z) and the conformation (s-cis) of compounds 1-2 obtained were established by an NMR study and unequivocally set by nuclear Overhauser effect difference experiments. An X-ray structure of compound 1e is also reported, showing a strong intramolecular NH.N hydrogen bond. Ab initio calculations (HF/3-21G and HF/3-21+G) have been carried out on several representative examples (1e, 1p, and 1l) in an attempt to support and provide the correct geometry of these derivatives. Structural considerations among the possible isomers of compounds 1 are discussed. From these studies it was concluded that the theoretical calculations agree with the experimental results. In addition, a very simple one-pot procedure for the preparation of masked N-substituted alpha-alkylated beta-enamino acid derivatives 2 from 6, 7, and different alkyl halides (R(3)Y) is described.

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Section: Introductionmentioning

confidence: 99%

An Efficient and Simple Entry toN-Substituted β-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines

Fustero

Navarro²,

Díaz³

et al. 1996

J. Org. Chem.

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“…However, from experiments carried out within our group, the process appears to be suitable only for acyclic methyl ketimines. In contrast, cyclic methyl ketimines (entry 17, Table ) and other nonmethyl derivatives, for instance ketimines derived from propiophenone, were unreactive under the same reaction conditions.…”

Section: Resultsmentioning

confidence: 97%

“…In this paper, we wish to describe a new and simple method for the synthesis of N -substituted β-enamino imidazole carbonylic derivatives 2 by reaction of ketimines 1 , derived from aliphatic or aromatic amines, with N , N ‘-carbonyldiimidazole (CDI) . In addition, one- and two-step general procedures for preparing N -substituted β-enamino esters and thioesters 4 have been developed.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters

et al. 1998

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A new strategy has been developed for the synthesis of several β-enamino acid derivatives. N,N‘-Carbonyldiimidazole has been used as C-acylating agent of methyl ketimines, providing a direct and simple route to new β-enamino carbonyl imidazole derivatives 2. These derivatives 2 were cleanly and efficiently transformed into β-enamino esters 4 (X = O) and thioesters 4 (X = S) by reaction with a great variety of alcohols and thiols, including tertiary ones. Alternative and complementary routes to compounds 4 were also investigated. In addition, β-keto esters 6 have been obtained by mild acid hydrolysis of β-enamino esters 4.

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N,N′-Carbonyldiimidazole

Armstrong¹,

Li²

2007

Encyclopedia of Reagents for Organic Synthesis

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A new method for the regioselective synthesis of β-enamino acid derivatives

Cited by 9 publications

References 21 publications

An Efficient and Simple Entry toN-Substituted β-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines

An Efficient and Simple Entry toN-Substituted β-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines

Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters

N,N′-Carbonyldiimidazole

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