Michael Addition of Nitroalkanes to Dimethyl Citraconate, with DBU as Base: An Unexpected, One-Pot Synthesis of Polyfunctionalized Carbonyl Derivatives

Abstract

Michael addition of nitroalkanes to dimethyl citraconate, with DBU as base, allows the one pot formation of keto diesters. The reaction proceeds through an equilibrium form of the acceptor, followed by Michael addition of the nitroalkane and then, in situ Nef conversion.

Key words

DBU - Nef reaction - keto esters - nitroalkanes - dimethyl citraconate

References

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8

PM3 semiempirical calculations by using the Gaussian 94W package showed that 9 is more stable than 6 by 2.0 kcal/mol. Gaussian 98 (Revision A.7): Frisch M. J., Trucks G. W., Schlegel H. B., Scuseria G. E., Robb M. A., Cheeseman J. R., Zakrzewski V. G., Montgomery J. A. Jr., Stratmann R. E., Burant J. C., Dapprich S., Millam J. M., Daniels A. D., Kudin K. N., Strain M. C., Farkas O., Tomasi J., Barone V., Cossi M., Cammi R., Mennucci B., Pomelli C., Adamo C., Clifford S., Ochterski J., Petersson G. A., Ayala P. Y., Cui Q., Morokuma K., Malick D. K., Rabuck A. D., Raghavachari K., Foresman J. B., Cioslowski J., Ortiz J. V., Baboul A. G., Stefanov B. B., Liu G., Liashenko A., Piskorz P., Komaromi I., Gomperts R., Martin R. L., Fox D. J., Keith T., Al-Laham M. A., Peng C. Y., Nanayakkara A., Gonzalez C., Challacombe M., Gill P. M. W., Johnson B., Chen W., Wong M. W., Andres J. L., Gonzalez C., Head-Gordon M., Replogle E. S., Pople J. A.; Gaussian 98 (Revision A.7); Gaussian, Inc.: Pittsburgh PA, 1998;

13

Selected analytical data for the compounds 8h,i. 8h: IR: 3412, 1738 cm^-1; ¹H NMR (CDCl₃): δ = 1.3-1.6 (m, 6 H), 2.42 (bt, 2 H, J = 7.0 Hz), 2.56 (dd, 1 H, J = 16.6 and 6.7 Hz), 2.62 (dd, 1 H, J = 17.7 and 6.1 Hz), 2.68 (dd, 1 H, J = 16.5 and 6.4 Hz), 2.91 (dd, 1 H, J = 18.0 and 7.0 Hz), 3.2-3.3 (m, 1 H), 3.6-3.7 (m, 2 H), 3.65 (s, 3 H), 3.66 (s, 3 H); ¹³C NMR (CDCl₃): δ = 23.3, 25.2, 32.4, 35.1, 36.3, 42.7, 43.1, 51.9, 52.2, 62.5, 172.0, 174.1, 208.3; MS (EI, 70 eV)
m/z 278 (M⁺ + 4), 257, 243, 187, 170, 127 (100%), 69, 55, 41, 31. 8i: IR: 1741 cm^-1; ¹H NMR (CDCl₃): δ = 2.14 (s, 3 H), 2.56 (dd, 1 H, J = 16.8 and 6.3 Hz), 2.6-2.8 (m, 6 H), 2.96 (dd, 1 H, J = 18.6 and 6.6 Hz), 3.2-3.3 (m, 1 H), 3.65 (s, 3 H), 3.66 (s, 3 H); ¹³C NMR (CDCl₃): δ = 30.3, 35.5, 36.6, 36.8, 37.4, 43.6, 52.3, 52.7, 172.5, 174.5, 207.2, 207.4; MS (EI, 70 eV) m/z 259 (M⁺ + 1), 226, 187, 127, 99 (100%), 59, 43, 29.