Ozone reacts very smoothly with acetals to give the corresponding esters. There are six gauche conformations that are theoretically possible for an acetal function. It is shown that only three of them are reactive toward ozone. It is proposed that a reactive acetal function must take a conformation in which each oxygen must have an electron pair orbital oriented antiperiplanar to the C—H bond. The mechanism of this reaction is also discussed.

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 theorientation ofthe lone pair orbitals of the heteroatoms governs this remarkable selective decomposition.L'hydrolyse basique des sels d'imidate N-disubstitues passe par la formation d'un intermtdiaire tetrahedrique du type hemi-orthoamide qui peut conduire soit aux produits amide-alcool ou ester-amine. Les rksultats experimentaux obtenus dkmontrent que la conformation precise de I'intermediaire tttrahkdrique determine la formation des produits. 11 est de plus avancC que I'orientation des orbitales d'electrons non-lies des httCroatomes contrBle la dtcomposition selective de l'intermkdiaire tetrahkdrique.Can. J . Chem.. 51. 1665 (1973) We have recently demonstrated the impor-amide-alcohol products 3 via a kinetically contance of the conformation of the tetrahedral trolled reaction, no information on the orbital intermediate (hemi-orthoester) during the hydrolysis or the transesterification of esters (1).We now wish to report that the conformation of the tetrahedral intermediate (hemi-orthoamide) formed during the hydrolysis of ainide and related functions is equally important; speclfic cleavage of a carbon-oxygen or a carbon-nitrogen bond being allowed only if the other two heteroatoms (oxygen or nitrogen) of the tetrahedral intermediate have each an orbital oriented antiperiplanar to the leaving 0-alkyl or N-alkyl group. In order to verify this stereoelectronic theory, we have selected for study the basic hydrolysis of the N-disubstituted imidate salts 1 (2) (Scheme I), expecting that such salts would react very fast with hydroxide ion to yield a tetrahedral intermediate 2 which can give in principle the amide-alcohol products 3 or the ester-amine products 4.3 If the reaction gives the

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.L'hydrolyse ou la transesterification d'un ester procede par un intermediaire tetrahtdrique du type hemiorthoester. I1 y a 9 conformtres gauches possibles pour un hemi-orthoester et il est propose que chaque conformere se decompose d'une maniere tres selective. I1 est de plus avance que les orbitales d'electrons non-lies des atomes d'oxygtne contrglent cette dtcomposition selective.

Six gauche conformations are theoretically possible for an acetal function and only three of them are reactive toward ozone. Each oxygen of the acetal function must have an electron pair orbital oreitned antiperiplanar to the C—H bond in order to be reactive toward ozone.

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