The Mechanism of Hydrolysis of Imidate Salts. The Importance of Stereoelectronic Control and pH of the Reaction Medium on the Cleavage of Tetrahedral Intermediates

1975 ◽  
Vol 53 (20) ◽  
pp. 3029-3037 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Roland J. Taillefer
Keyword(s):  
Conformational Changes ◽  
Entire Range ◽  
Reaction Medium ◽  
Tetrahedral Intermediate ◽  
Mechanism Of Hydrolysis ◽  
Stereoelectronic Control ◽  
Neutral Conditions ◽  
Hydrolysis Of ◽  
Ionic Forms ◽  
Tetrahedral Intermediates

Hydrolysis of anti imidate salts give the ester amine products exclusively over the entire range of pH. Hydrolysis of syn imidate salts in acidic and neutral conditions give the ester amine products only; in basic conditions, mixtures of ester amine and amide alcohol products are observed. These results are explained by the application of the new theory of stereoelectronic control on the various ionic forms T+, T±, and T− of the tetrahedral intermediate. For syn imidate salts, conformational changes of the tetrahedral intermediate must occur in order to have cleavage with stereoelectronic control.

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.

ChemInform Abstract: THE HYDROLYSIS OF CYCLIC ORTHOESTERS. STEREOELECTRONIC CONTROL IN THE CLEAVAGE OF HEMIORTHOESTER TETRAHEDRAL INTERMEDIATES

1975 ◽  
Vol 6 (38) ◽  
pp. no-no
Author(s):  
PIERRE DESLONGCHAMPS ◽  
ROBERT CHENEVERT ◽  
ROLAND J. TAILLEFER ◽  
CLAUDE MOREAU ◽  
JOHN K. SAUNDERS
Keyword(s):  
Stereoelectronic Control ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

Hydrolysis of cyclic unsymmetrical anti imidate salts. New evidence for stereoelectronic control

1979 ◽  
Vol 57 (24) ◽  
pp. 3262-3271 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Ukken Ouseph Cheriyan ◽  
Roland J. Taillefer
Keyword(s):  
Ammonium Salt ◽  
Controlled Conditions ◽  
Kinetically Controlled ◽  
Stereoelectronic Control ◽  
Acidic Conditions ◽  
New Evidence ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates ◽  
Hydrogen Bonded

The synthesis and the hydrolytic behavior of the cyclic imidate salts 7, 8, and 9 is reported. Under acidic conditions, the salt 7 gives the ester ammonium salt 21 and the salt 9 gives a 1:1 mixture of the ester ammonium salt 22 and the amide alcohol 23 as the rotamer 23B only. Under basic conditions, the salt 7 (or 8) gives a 2:8 (or 1:9) mixture of the amide alcohol rotamers 25A and 25B (or 27A and 27B) under kinetically controlled conditions. The salt 9 gives, as the kinetic product, the amide alcohol rotamer 23B only. These results can be rationalized on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates and by taking into account that the nitrogen in 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 a C—N bond.

The Hydrolysis of Cyclic Orthoesters. Stereoelectronic Control in the Cleavage of Hemiorthoester Tetrahedral Intermediates

1975 ◽  
Vol 53 (11) ◽  
pp. 1601-1615 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Robert Chênevert ◽  
Roland J. Taillefer ◽  
Claude Moreau ◽  
John K. Saunders
Keyword(s):  
Experimental Evidence ◽  
Acid Hydrolysis ◽  
Alkoxy Group ◽  
Gauche Conformer ◽  
Group A ◽  
Stereoelectronic Control ◽  
Hydroxy Esters ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The synthesis of several cyclic dialkoxy orthoesters is reported. Acid hydrolysis of these orthoesters under kinetically controlled conditions gives the corresponding hydroxy esters only. Conformationally rigid cyclic mixed orthoesters give a hydroxy ester by exclusive loss of the axial alkoxy group. A cyclic orthoester can have nine different gauche conformations. It is shown that they are hydrolyzed through only one gauche conformer. These results bring further experimental evidence that there is a stereoelectronic control in the cleavage of tetrahedral intermediates in the hydrolysis of esters.

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.

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