The Hydrolysis of Imidate Salts. Stereoelectronic Control in the Cleavage of the Hemiorthoamide Tetrahedral Intermediate

1975 ◽  
Vol 53 (18) ◽  
pp. 2791-2807 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Serge Dubé ◽  
Claude Lebreux ◽  
Dennis R. Patterson ◽  
Roland J. Taillefer
Keyword(s):  
Alkyl Group ◽  
Lone Pair ◽  
The Other ◽  
Tetrahedral Intermediate ◽  
Hydrolysis Products ◽  
Anti Conformation ◽  
Stereoelectronic Control ◽  
Basic Hydrolysis ◽  
Hydrolysis Of ◽  
Nitrogen Bond

A new stereoelectronic theory for the cleavage of the tetrahedral intermediate (hemiorthoamide) in the hydrolysis of amides is presented. In this new theory, the precise conformation of the tetrahedral intermediate controls the nature of the hydrolysis products. It is postulated that the breakdown of the tetrahedral intermediate depends upon the orientation of the lone pair orbitals of the heteroatoms. Specific cleavage of a carbon–oxygen or a carbon–nitrogen bond in any conformer is allowed only if the other heteroatoms (oxygen and nitrogen) each have an orbital oriented antiperiplanar to the leaving O-alkyl or N-alkyl group. Experimentally, a study of the basic hydrolysis of a variety of N,N-dialkylated imidate salts having either a syn or an anti conformation demonstrates clearly that there is a stereoelectronic control in the cleavage of the hemiorthoamide.

The Importance of Conformation of the Tetrahedral Intermediate in the Hydrolysis of Amides. Selective Cleavage of the Tetrahedral Intermediate Controlled by Orbital Orientation

1973 ◽  
Vol 51 (10) ◽  
pp. 1665-1669 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Claude Lebreux ◽  
Roland Taillefer
Keyword(s):  
Experimental Evidence ◽  
Lone Pair ◽  
Tetrahedral Intermediate ◽  
Basic Hydrolysis ◽  
Hydrolysis Of ◽  
Orbital Orientation

The basic hydrolysis of N-disubstituted imidate salts proceeds via a hemi-orthoamide tetrahedral intermediate which can in principle give amide–alcohol or ester–amine products. Experimental evidence has been obtained which shows that the specific conformation of the tetrahedral intermediate determines products formation and it is further suggested that the orientation of the lone pair orbitals of the heteroatoms governs this remarkable selective decomposition.

A FACILE SYNTHESIS AND REACTIONS OF AMINO SELENOLO[2,3-b]PYRIDINE CARBOXYLATE

2015 ◽  
Vol 12 (1) ◽  
pp. 3910-3918 ◽  
Author(s):  
Dr Remon M Zaki ◽  
Prof Adel M. Kamal El-Dean ◽  
Dr Nermin A Marzouk ◽  
Prof Jehan A Micky ◽  
Mrs Rasha H Ahmed
Keyword(s):  
Biological Activity ◽  
Carbonyl Compounds ◽  
Mass Spectra ◽  
The Other ◽  
Pyridine Derivatives ◽  
Facile Synthesis ◽  
High Biological Activity ◽  
Basic Hydrolysis ◽  
Pyridine Carboxylate ◽  
Hydrolysis Of

 Incorporating selenium metal bonded to the pyridine nucleus was achieved by the reaction of selenium metal with 2-chloropyridine carbonitrile 1 in the presence of sodium borohydride as reducing agent. The resulting non isolated selanyl sodium salt was subjected to react with various α-halogenated carbonyl compounds to afford the selenyl pyridine derivatives 3a-f  which compounds 3a-d underwent Thorpe-Ziegler cyclization to give 1-amino-2-substitutedselenolo[2,3-b]pyridine compounds 4a-d, while the other compounds 3e,f failed to be cyclized. Basic hydrolysis of amino selenolo[2,3-b]pyridine carboxylate 4a followed by decarboxylation furnished the corresponding amino selenolopyridine compound 6 which was used as a versatile precursor for synthesis of other heterocyclic compound 7-16. All the newly synthesized compounds were established by elemental and spectral analysis (IR, 1H NMR) in addition to mass spectra for some of them hoping these compounds afforded high biological activity.

ChemInform Abstract: HYDROLYSIS OF IMIDATE SALTS STEREOELECTRONIC CONTROL IN THE CLEAVAGE OF THE HEMIORTHOAMIDE TETRAHEDRAL INTERMEDIATE

1975 ◽  
Vol 6 (51) ◽  
pp. no-no
Author(s):  
PIERRE DESLONGCHAMPS ◽  
SERGE DUBE ◽  
CLAUDE LEBREUX ◽  
DENNIS R. PATTERSON ◽  
ROLAND J. TAILLEFER
Keyword(s):  
Tetrahedral Intermediate ◽  
Stereoelectronic Control ◽  
Hydrolysis Of

The products of hydrolysis of cyclic orthoesters as a function of pH and the theory of stereoelectronic control

1985 ◽  
Vol 63 (9) ◽  
pp. 2485-2492 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Jean Lessard ◽  
Yves Nadeau
Keyword(s):  
Acid Hydrolysis ◽  
Hydroxy Ester ◽  
The Other ◽  
Relative Percentage ◽  
Stereoelectronic Control ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The acid hydrolysis of cyclic orthoesters 1, 3–6 (R = Me), and 2 (R = Me and Et) as a function of pH was studied. The bicyclic orthoester 5 yields mainly the hydroxy-ester (less than 5% lactone), and this result is essentially independent of pH. For the other orthoesters, the relative percentage of products differs for each case and varies with pH. At pH ≤ 3, the percentage of lactone is always larger than at pH > 3. These results are explained on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates.

Basic hydrolysis of some N-phenylcarbamates and basic methanolysis of some N-phenylacetamides containing an ortho nitro substituent

1984 ◽  
Vol 37 (10) ◽  
pp. 2005
Author(s):  
TJ Broxton
Keyword(s):  
Induction Period ◽  
Nitro Group ◽  
Resonance Effect ◽  
Kinetic Studies ◽  
Bond Breaking ◽  
Hydroxide Ion ◽  
Tetrahedral Intermediate ◽  
Group Reaction ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

Kinetic studies of the basic methanolysis of N-(2-nitropheny1)acetamides indicate that unlike the 4-nitro isomer, no change of mechanism occurs on inclusion of an N-methyl group. Reaction occurs with rate-determining C-N bond breaking for both the N-H and N-methyl compounds. Basic hydrolysis of some methyl N-(2-nitropheny1)carbamates occurred by the BAC2 mechanism and the tetrahedral intermediate formed during the hydrolysis decomposed with preferential C-O bond breaking. This is in contrast to the basic hydrolysis of methyl N-methyl-N-4-nitrophenyl- carbamate, which has previously been shown to occur with preferential C-N bond breaking. For the hydrolysis of methyl N-methyl-N-(2-nitrophenyl)carbamate, an induction period in amine production was detected at 0.45 M hydroxide ion. This was interpreted to mean that the tetrahedral intermediate breaks down by loss of methoxide ion. At 0.93 M hydroxide ion, however, no induction period in amine production was observed. The possibility of reaction through a dianionic intermediate was raised to explain this observation. The amide ion (2-NO2C6H4NMe-) is a poorer leaving group than its 4-nitro isomer. This is explained by steric crowding in the 2-nitro compound, resulting in twisting of the nitro group out of the plane of the benzene ring and a consequent reduction in the electron-withdrawing resonance effect of the 2-nitro group compared to the 4-nitro group.

Hydrolytic behavior of two β-lactams and their corresponding imidate salts. New evidence for stereoelectronic control

1980 ◽  
Vol 58 (19) ◽  
pp. 2061-2068 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Maurice Caron
Keyword(s):  
Sodium Hydroxide ◽  
Carbonyl Oxygen ◽  
Oxygen Exchange ◽  
Hydrochloride Salt ◽  
Stereoelectronic Control ◽  
Acidic Conditions ◽  
Basic Hydrolysis ◽  
New Evidence ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The basic hydrolysis and the concurrent carbonyl–oxygen exchange of 18O-labelled N-phenyl-4-phenyl-2-azetidinone (5*) and N-2,6-dimethylphenyl-2-azetidinone (6*) have been studied. β-Lactam 5* was easily hydrolysed and showed no carbonyl–oxygen exchange with 0.1 N sodium hydroxide (dioxane–water, 9:1). Under the same conditions, β-lactam 6* gave no exchange and was found resistant to basic hydrolysis. Hydrolysis and exchange was observed when 6* was refluxed with 0.1 N and 1 N sodium hydroxide in water.The hydrolysis of the corresponding imidate salts 7 and 8 was also investigated. Under basic conditions, salt 7 gave an 8:2 mixture of ester amine 9 and β-lactam 5, while under acidic conditions the hydrochloride salt of ester amine 9 was the only product. Under basic conditions, the imidate salt 8 produced only the β-lactam 6, and under acidic conditions, a 3:7 mixture of the hydrochloride salt of 10 and β-lactam 6. Under stronger acidic conditions (≥3 N HCl), 8 gave only the starting β-lactam 6.The results of these hydrolysis reactions are easily explained on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates, and by taking into account that the nitrogen of tetrahedral intermediates must be either protonated under acidic conditions, or hydrogen bonded with the solvent under basic conditions in order to observe the cleavage of the C—N bond.

The Importance of Conformation of the Tetrahedral Intermediate in the Hydrolysis of Esters. Selective Cleavage of the Tetrahedral Intermediate Controlled by Orbital Orientation

1972 ◽  
Vol 50 (20) ◽  
pp. 3405-3408 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Paul Atlani ◽  
Daniel Fréhel ◽  
Alain Malaval
Keyword(s):  
Lone Pair ◽  
Tetrahedral Intermediate ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Orbital Orientation ◽  
Oxygen Atoms

The hydrolysis or the transesterification of esters proceeds via a hemi-orthoester tetrahedral intermediate. There are nine different gauche conformers possible for such a tetrahedral intermediate and it is proposed that each of them should decompose in a highly selective manner. It is further proposed that the lone pair orbitals of the oxygen atoms control this selective decomposition.

Micellar catalysis of organic reactions. XII. Basic hydrolysis of some alkyl and aryl N-(4-Nitrophenyl)carbamates

1984 ◽  
Vol 37 (1) ◽  
pp. 47 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Kinetic Studies ◽  
Micellar Catalysis ◽  
Organic Reactions ◽  
Bond Breaking ◽  
Tetrahedral Intermediate ◽  
Stable Product ◽  
Methyl Derivatives ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

The basic hydrolysis of a number of alkyl and aryl N-(4-nitrophenyl)carbamates in the presence and absence of micelles of cetyltrimethylammonium bromide (ctab) are reported. In water the stable product at 26�C was N-(4-nitrophenyl)carbamate ion (3). At higher temperatures this carbamate ion slowly decomposed to 4-nitroaniline. In ctab the decarboxylation of the N-(4-nitrophenyl)carbamate ion was strongly catalysed (× 45) and thus the observed final product even at 26�C was 4-nitroaniline. Kinetic studies in water and in ctab were consistent with decomposition of the methyl carbamate (la) by a BAC2 mechanism and the 2,2,2-trifluoroethyl carbamate (lc) by an E1cB mechanism. The extent of ionization of the substrate carbamates to nitranion (4) was enhanced in ctab as was the rate of spontaneous decomposition of the nitranion. This is in contrast to other E1cB reactions reported in the literature, for which the rate of spontaneous decomposition of the carbanion was inhibited by ctab. For compounds reacting by the BAC2 mechanism, the tetrahedral intermediate (2) partitioned in favour of C-OR bond breaking rather than C-N bond breaking observed previously for some N-methyl derivatives.

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