AB-INITIO MOLECULAR-ORBITAL STUDY OF REACTIVITY OF ACTIVE ALKYL-GROUPS .3. NITROSATION OF ACYCLIC CARBONYL COMPOUND WITH METHYL NITRITE VIANA-STATE( CHELATED TRANSITION)

The mechanism of the nitrosation of sodium enolate of acetone [CH3COCH 2]Na--(+) (1) with methyl nitrite CH3ONO (2) to give 1-hydroxy-imino-2 -oxo-propane CH3COCH=NOH (3) was studied by the ab initio molecular or bital (MO) method. The complex [CH3COCH2NO(OCH3)]Na--(+) (C-II) was fi rst formed from the adduct (C-I) of 1 and 2 through the pericyclic tra nsition state (TS1). Finally, Z-hydroxyimino compound (3Z) was obtaine d through demethoxylation of 2 moiety and abstraction of an active hyd rogen atom in C-II with a base, In the final formation of 3Z, two leav ing groups, the methoxy group and the active hydrogen atom in C-II, sh ould be situated in positions with respect to each other which permit their elimination, i.e., they are antiperiplanar to one another. It ha s become apparent that 3Z tends to be formed predominantly when a coun teraction of a base coordinates to the oxygen atom of the enolate of a cetone.