Conformational studies of alkyl nitrites, using low-temperature carbon-13, oxygen-17, and nitrogen-14 NMR spectroscopy. Oxygen-17 NMR of N-substituted formamides

Pawar, Diwakar M.; Mark, Hugh L.; Hosseini, H.; Harris, Yolanda; Noe, Eric A.

doi:10.1021/j100131a015

Cited by 7 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The proportion of the anti-form of RЉONO was found to increase in the order RЉϭCH 3 Ͻpri-maryϽsecondaryϽtertiary. 5) The E/Z ratio of the hydroxyimino compound increased when methyl nitrite (3) was used in place of tert-butyl nitrite in the nitrosation of 5, 6) which indicated that the E/Z ratio is affected by the conformation of RЉONO. Our experimental and theoretical investigations on the mechanisms of nitrosation have shown that the E/Z ratio varied significantly with the participation of the counter cation M ϩ of the base catalyst.…”

mentioning

confidence: 97%

Ab Initio Molecular Orbital Study of the Reactivity of Active Alkyl Groups. V. Nitrosation Mechanism of Acetone with syn-Form of Methyl Nitrite.

Niiya

Ikeda

Yukawa

et al. 2002

CHEMICAL & PHARMACEUTICAL BULLETIN

View full text Add to dashboard Cite

For the nitrosation of active alkyl compounds RCOCH 2 RЈ using alkyl nitrite RЉONO in the presence of base catalyst B Ϫ M ϩ to give E-and Z-hydroxyimino compound RCOCRЈϭ NOH (Eq. 1), the rate-determining step of the nitrosation is the C-N bond formation.In the case of the nitrosation of the methyl or ethyl group of carbonyl compounds, such as acetone and 2-butanone, the E-form of the hydroxyimino compound was predominantly obtained. [1][2][3] On the other hand, a E-form/Z-form (E/Z) ratio of 2.3 was observed for the nitrosation of 3-methyl-1-phenylbutan-1-one (PhCOCH 2 CH(CH 3 ) 2 ) (5) with tert-butyl nitrite in THF. 4) Thus the E/Z ratio decreased with increasing bulkiness of the R and RЈ groups of RCOCH 2 RЈ.As shown in Fig. 1, alkyl nitrite RЉONO exists as either the syn-or anti-conformer. The proportion of the anti-form of RЉONO was found to increase in the order RЉϭCH 3 Ͻpri-maryϽsecondaryϽtertiary.5) The E/Z ratio of the hydroxyimino compound increased when methyl nitrite (3) was used in place of tert-butyl nitrite in the nitrosation of 5, 6) which indicated that the E/Z ratio is affected by the conformation of RЉONO. Our experimental and theoretical investigations on the mechanisms of nitrosation have shown that the E/Z ratio varied significantly with the participation of the counter cation M ϩ of the base catalyst. 4,7,8) Consequently, two types of transition state models (TS) during the C-N bond formation process were proposed to elucidate the variation of the E/Z ratio in various solvents; specifically, the TS models were 1) metal-chelated pericyclic transition state (TS CHELATED ) and 2) open-chain transition state without metal (TS OPEN ). In the present study, the mechanisms of the stereochemical nitrosation of 1 or 2 with syn-form of 3 (syn-3), as opposed to anti-3, were investigated by ab initio MO methods using the same two transition state models as described above. 4,7)Our studies have shown the predominant formation of 4E when the complex [CH 3 COCH 2 NO(OCH 3 )] Ϫ Na ϩ was produced via TS CHELATED , with the O 3 atom of syn-3 coordinated to the Na ϩ atom of 1. On the other hand, similar coordination between the O 3 atom of anti-3 to the Na ϩ atom of 1 was not observed in TS, as described in the previous paper. 4) ExperimentalComputational Procedures MO calculations were carried out using the Gaussian 98 program.9) The optimized geometries in the TS were initially determined using HF/6-31G, followed by intrinsic reaction coordinate (IRC) calculations. For the energies of the complexes, calculations were performed using similar methods, MP3/6-31ϩG//HF/6-31G, as previously described. 4)The structure of syn-3 was used to provide the initial geometries for the C-N bond formation process. Results and DiscussionFor the studies on the nitrosation mechanisms between 3 and 1 or 2, TS CHELATED or TS OPEN models, respectively, were adopted for the C-N bond formation process. In this report, the influence of the conformation of alkyl nitrite on the nitrosation mechanism was investigated using syn-3, as o...

show abstract

mentioning

confidence: 97%