Dialkylation of diesters

Synthesis (Germany)

Volumn 1986, Issue 7, 1986, Pages 552-554

  Weagley, Ronald J ^a   Gibson, Harry W ^a  

^a XEROX CORPORATION   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 30244495713     PISSN: 00397881     EISSN: 1437210X     Source Type: Journal    
DOI: 10.1055/s-1986-31698     Document Type: Article

References (11)

1. Blaise, E., Marcilly, L. Bull. Soc. Chim. Fr. 1903, 31, 110-115.
2. Mikhailov, M., Dirlikov, S., Schneider, B, Stokr, J. Dokl. Bulg. Akad. Nauk 1971, 24, 1333-1336; C.A. 1972, 76, 127694d.
3. Cregge, R.J., Hermann, J.L, Lee, C.S., Richman, J.E, Schles-singer, R.H. Tetrahedron Lett. 1973, 2425-2428.
4. Dictionary of Organic Compounds, Oxford Univ. Press, New York, 1979, p 3176.
5. Vancea, L., Bywater, S. Macromol. 1981, 14, 1776-1778.
6. The diacid was prepared in 92-97 % crude yields from norbor-nene on a 0.2 molar scale by oxidation with NaJ04 and Ru02 [Clark, R.D, Org. Prep Proced. Int. 1974, 6, 49-51].
7. The dimethyl ester was prepared in 90% pure yield from the diacid using HQ and dimethoxypropane [Playtis, A. J., Fissekis, J.D. J. Org. Chem. 1975, 40, 2488-2495].
8. Addition of the diester to lithium diisopropylamide resulted in a precipitate (monoanion?). Addition of the methyl iodide led to its dissolution.
9. Nakanishi, K. Infrared Absorption Spectroscopy, Holden-Day, San Francisco, 1964, p. 20.
10. N.M.R. assignments assume that the methyl groups occupy pseudo-equatorial positions in preference to methoxycarbonyl groups (by ~ 0.5 kcal/mol) and that equatorial methyl groups appear downfield from axial methyl groups (Eliel, E. L, Allinger, N.L., Angyal, S.J., Morrison, G.A, Conformational Analysis, Interscience Publishers, New York, 1965, pp 152ff, 200ff, 440, 441). In 10, however, the methyl/methoxycarbonyl bias toward equatorial methyl is dominated by the methoxycarbonyl/hydrogen bias toward equatorial methoxycarbonyl (1.1 kcal/mol), yielding a predominantly axial methyl time averaged spectrum. For 11 both substituent biases (CHj/COOCH, and COOCHj/H) favor equatorial methyl. Thus the methyl signal of 11 is expected to be downfield from that of 10. The methyl groups of 8 are assumed to appear at lower field than those of 9.
11. In 10 the methoxycarbonyl groups are non-equivalent. This is also true in 11. Thus in a mixture of 10 and 11, four possible OCH3 signals could in principle result. Apparently three of these are approximately isochronous. The upfield signal is probably that of the predominantly axial quaternary methoxycarbonyl group of 11, while the downfield signal contains the predominantly equatorial methoxycarbonyl group of 10. See Ref.9 and chemical shifts of methoxycarbonyl groups in 8 and 9.