Geometric isomers of O-alkylbenzohydroximoyl chlorides. Synthesis, identification, and acid-catalyzed isomerization

Johnson, James E.; Nalley, E. Ann; KUNZ, Y. K.; Springfield, John

doi:10.1021/jo00864a015

Cited by 36 publications

(33 citation statements)

References 5 publications

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“…In a study of geometric isomerism of O-alkylbenzhydroximates, Johnson and co-workers 10,15 noted that 1 H chemical shifts of the O-alkyl group hydrogens are larger in the Z isomer than in the E isomer (in chloroform solutions). Our results confirm this finding (irrespective of solvent) and also show that the opposite observation regarding the shifts in benzimidoyl chlorides was not correct because of the erroneous assignment of isomeric structures.…”

Section: Resultsmentioning

confidence: 99%

“…and can be separated, was established by x-ray diffraction. 13,14 E/Z isomer assignment of liquid compounds 2 and 3 has been supported by a number of experimental methods, 10,15 including chemical properties, dipole moment measurements and 1 H NMR spectra, as compared with similar properties of 1 and 4.…”

Section: Methodsmentioning

confidence: 92%

“…10 Similarly, the described photoisomerization procedure 10 was used for transformation to their geometric isomers (1E and 2E) except that chloroform was used as a solvent for 1. (Z)-Methyl N-methoxybenzoximidate (3Z) was prepared from the corresponding N-methoxybenzimidoyl chloride by reaction with sodium methanolate; 10 it was converted to the E isomer (3E) in HCl-benzene mixture according to the literature. 10 The preparation of 4Z and 4E was described earlier.…”

Section: Experimental Synthesismentioning

confidence: 99%

“…(Z)-Methyl N-methoxybenzoximidate (3Z) was prepared from the corresponding N-methoxybenzimidoyl chloride by reaction with sodium methanolate; 10 it was converted to the E isomer (3E) in HCl-benzene mixture according to the literature. 10 The preparation of 4Z and 4E was described earlier. 5 The physical constants of the prepared compounds agreed with those in the literature.…”

Section: Experimental Synthesismentioning

confidence: 99%

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NMR study of E/Z isomerism in N‐alkoxybenzoimidic acid derivatives

Schraml

Blechta

Karban

et al. 2002

Magnetic Reson in Chemistry

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Well defined E/Z isomers of N-methoxy-p-nitrobenzimidoyl chloride, N-methoxybenzimidoyl chloride, methyl N-methylbenzohydroximate and ethyl N-hydroxybenzimidate were prepared in order to provide model data for studies of benzhydroximic acid derivatives and related compounds. NMR parameters [ 1 H, 13 C and 15 N chemical shifts and 1 J. 13 C, 13 C/ coupling constants] were determined. The results show that stereochemically most significant are the values of 1 J. 13 C, 13 C/ couplings between aromatic C ipso and C N carbons and that the relationship, jJ cis j > jJ trans j, known for this coupling from oximes, is not affected by electronegative substituents at the C N carbon atom, but the values are.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 92%

Section: Experimental Synthesismentioning

confidence: 99%

Section: Experimental Synthesismentioning

confidence: 99%

See 2 more Smart Citations

NMR study of E/Z isomerism in N‐alkoxybenzoimidic acid derivatives

Schraml

Blechta

Karban

et al. 2002

Magnetic Reson in Chemistry

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“…It is known [11][12][13][14][15] that the 4,5-disubstituted oxazolidinones exhibiting signals for 4-H and 5-H at lower field have cis-structure while the 4,5-disubstituted oxazolidinones showing those at higher field have trans-structure. From the fact that signals due to 4-H and 5-H of oxazolidinone 13 (4-H: d 5.50; 5-H: d 5.74) appeared in down-field compared with those of isomer 13 (4-H: d 5.10; 5-H: d 5.47), we deduced the former as cis-and the latter as trans-isomers, respectively.…”

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confidence: 99%

Stereoselective Synthesis of .BETA.-Hydroxyphenylalanines Using Imino 1,2-Wittig Rearrangement of Hydroximates

Miyata

Asai

Naito

2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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b-Hydroxy-a-amino acids are an important class of amino acids that are found in nature and as constituents of more complex natural products. 1-7) For example, b-hydroxytyrosine and b-hydroxyphenylalanine derivatives are found in clinically important glycopeptide antibiotics, such as Vancomycin and Teicoplanin. In addition, Lysobactin, which has shown antibiotic activity, contains five b-hydroxy-a-amino acids unit in the molecule. These densely functionalized amino acids are also useful building blocks for synthesis of b-lactams and sugars. Therefore, the synthesis of polypeptides and antibiotics containing b-hydroxy-a-amino acids are of interest to both synthetic and medicinal chemists. In recent years, we have developed a new imino 1,2-Wittig rearrangement of hydroximates which proceeds smoothly under basic conditions to give 2-hydroxyoxime ethers. [8][9][10][11] Part of the synthetic potentiality was demonstrated by the preparation of biologically important amino alcohols and the efficient synthesis of Cytoxazone. 11) In this paper, we disclose a new convenient methodology for the preparation of b-hydroxy-a-amino acids using imino 1,2-Wittig rearrangement of hydroximates. Our approach is shown in Chart 1. We chose the hydroximates 1a-c having ester, furan, and oxazoline moieties as substrates for imino 1,2-Wittig rearrangement. These functional groups are expected to readily convert into a carboxyl group. The hydroximates 1a-c are treated with LDA to give 2-hydroxyoxime ethers 2 which are subjected to stereoselective reduction of imine moiety to afford both the threo-and erythro-amino alcohols 3. Finally, the conversion of ester, furan, and oxazoline moieties into a carboxylic acid gives b-hydroxy-aamino acids 4. Results and DiscussionAt first, we examined the preparation of the Z-hydroximates 1a-c (Chart 2). According to the known procedure, 11-15) the acylation of methoxyamine hydrochloride with acid chloride 5a followed by treatment of the resulting amide 6a with carbon tetrabromide in the presence of triphenyl phosphine gave imidoyl bromides 7a which was then converted into hydroximate 1a by the treatment of sodium benzyloxide. Similarly, 1b was prepared by the bromination of 6b followed by the treatment of the resulting imidoyl bromide 7b with sodium benzyloxide. The hydroximate 1c was prepared from amino alcohol 8 16,17) via construction of oxazolidine ring, amidation, bromination, and benzyloxylation.Next, we investigated the 1,2-Wittig rearrangement reaction of hydroximates 1a-c with LDA (Chart 3, Table 1). Upon treatment with 4 eq. of LDA, the rearrangement of hydroximate 1b carrying furan ring proceeded smoothly at The imino 1,2-Wittig rearrangement of hydroximates containing a furan ring provides a novel method for the synthesis of b b-hydroxy-a a-amino acids. Upon treatment with LDA, hydroximates smoothly underwent the rearrangement to give Z-2-hydroxyoxime ethers in good yield, which were converted into both cis-and trans-oxazolidinones with high stereoselectivity. The cis-and trans-oxazolidino...

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