R. Baharfar, S.M. Baghbanian / Chinese Chemical Letters 23 (2012) 677–680
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smooth 2:1:1 addition reaction in 1,4-dioxane at ambient temperature, to produce highly functionalized 2,5-
diaminofuran derivatives 6 in 80–95% yields. The results are summarized in Scheme 1.
The structures of the isolated products 6a–i were deduced on the basis of IR, 1H and 13C NMR spectroscopy, mass
spectrometry, and elemental analysis. The mass spectrum of 6a displayed the molecular ion (M+) peak at m/z 478,
which are consistent with the 2:1:1 adduct of tert-butyl isocyanide, dimethyl acetylenedicarboxylate, and 1-
1
(carboxymethyl)uracil derivative. The H NMR spectrum of 6a in CDCl3 exhibited four single sharp lines readily
recognized as arising from two tert-butyl groups (d 1.37 and 1.47), two methoxy (d 3.78 and 3.89) protons. Along with
an AB system (JAB = 16.4 Hz) for two methylene group (d 4.42 and 4.48) protons. Two doublets were observed at d
5.73 and 7.15 (3JHH = 8.0 Hz) for the adjacent alkene protons, and the two broad singlets were observed at d 6.95 for
the NH of amine group and at d 8.73 for the NH of uracil ring. The 1H decoupled 13C NMR spectrum of 6a showed 18
distinct resonances in agreement with the aminofuran structure.
A mechanistic rationalization for this reaction is provided in Scheme 2. On the basis of the well-established
chemistry of isocyanides [19], it is reasonable to assume that the functionalized uracil based 2,5-diaminofurans 6 could
result from initial addition of the isocyanide to the acetylenic ester and subsequent protonation of the 1:1 adduct 7 by
carboxylic acid 3. Then, the positively charged ion 9 can be attacked by the carboxylate anion 8 to form imidoyl
carboxylate 10, which undergoes a Mumm rearrangement [6,20] under the reaction conditions employed, to produce
the a,b-unsaturated intermediate 11, followed by its trapping with isocyanide, to give the corresponding (2,4-dioxo-
3,4-dihydropyrimidin-1(2H)-yl)acetamido)-5-(tert-butylamino)furan-3,4-dicarboxylate derivatives.
1. Conclusions
In summary, we have described a novel, efficient, and simple method for the preparation of uracil based
diaminofuran derivatives of potential synthetic and pharmaceutical interest. In addition, the present procedure affords
advantages of good yields and a simple workup. Further investigation of the present method will be required to
establish its utility and scope.
Dimethyl 2-(N-tert-butyl-2-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamido)-5-(tert-butylamino)furan-3,4-
dicarboxylate (6a): Yellow oil, yield: 87%, IR (KBr) (nmax/cmÀ1): 3401 (NH), 1645 (C O). 1H NMR (400.13 MHz,
CDCl3): d 1.37 and 1.47 (2s, 18 H, 2Â t-Bu), 3.78 and 3.89 (2s, 6 H, 2Â OCH3), 4.42 and 4.48 (2d, 2H, AB system,
2JHH = 16.4 Hz, CH2), 5.73 (d, 1 H, 3JHH = .0 Hz, CH), 6.95 (br s, 1 H, NH t-Bu), 7.15 (d, 1 H, 3JHH = 8.0 Hz, CH),
8.73(br s, 1 H, NH). 13C NMR (100.6 MHz, CDCl3): d 27.9 and 29.7 (2Â CMe3), 50.2 (CH2), 51.3 and 52.7 (2Â
OCH3), 53.0 and 61.9 (2Â CMe3), 85.8 (C4 of furan), 102.0 (CH), 115.2 (C3 of furan), 136.4 (C5 of furan), 145.3 (CH),
150.7 (NCONH), 159.9 (C2 of furan), 163.5 and 163.6 (2Â CO2Me), 164.7 (NHCO), 167.9 (NCO). MS, m/z (%): 478
(6) [M+], 422 (25), 270 (25), 214 (73), 182 (30), 153 (35), 57 (100), 57 (60). Anal. Calcd. for C22H30N4O8: C, 55.22; H,
6.32; N, 11.71. Found: C, 55.27; H, 6.43; N, 11.60.
Acknowledgment
This research was supported by the Research Council of the University of Mazandaran, Iran.
Appendix A. Supplementary data
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