6762
A. Stadler et al. / Tetrahedron 57 ,2001) 6757±6763
1
1J137.2 Hz, C>CH3)3), 23.8 >q, J125 Hz, CH3). Anal.
calcd for C16H21NO4: C, 65.96; H, 7.26; N, 4.80; Found:
C, 65.97; H, 7.25; N, 4.72.
under N2-atmosphere and stirred overnight. The obtained
orange oil was dried on the vacuum line and afterwards
puri®ed by DCFC, using hexane/ethylacetate 3:2 as an
eluent. This yielded 0.36 g >32%) 10 as a yellow oil. IR
>Film): 2960, 1740 >ester carbonyl), 1650, 1620 cm21
4.2.3. 1-n-Butylamino-4,4-dimethyl-2-methoxycarbonyl-
pentan-1,3-dione 04c). 0.44 g of 2 and 0.2 g of n-butyl-
amine >under N2-atmosphere) yielded 0.13 g >21%, from
n-hexane) of 4c, mp: 888C; IR >KBr): 3270>H±N), 2980,
1
>CvO); H NMR >CDCl3): 1.33 >s, t-Bu), 3.88 >s, MeO),
6.36, 7.73 >dd, J8 Hz); Anal. calcd for C11H14O4: C, 62.85;
H, 6.71; Found: C, 62.96; H, 6.76. Signals related to 9 >see
Section 2): 1H NMR >CDCl3): 1.20>s, t-But), 1.42 >m, EtO),
3.75 >s, MeO), 3.90>q, EtO), 6.37 >d, cycl. CH2), 7.72 >m,
O±CH±O).
1755, 1715, 1645 cm21 >CvO); H NMR>CDCl3): 0.93 >t,
1
CH2±CH3), 1.25 >s, t-But), 1.35 >q, CH2±CH3), 1.50>q,
CH2±CH2), 3.25 >q, CH2±N), 3.73 >s, MeO), 5.02 >s,
H±C), 6.98 >s, H±N).
4.2.8. 2-t-Butyl-6-ethoxy-3-methoxycarbonyl-pyran-4-
one 011). 0.44 g of 2 were added to 0.33 g of ethoxyacetyl-
ene >50% solution in hexane) under N2 atmosphere. The
strong exothermic reaction was stirred at rt for 1 h, then
the reaction mixture was ¯ushed again with nitrogen and
stored over night at 2158C. The dark coloured mixture was
puri®ed by DCFC, using hexane/ethylacatate 2:1 as a
solvent. The obtained orange oil was dried by lyophilization
on the vacuum line, during that procedure it started to
solidify, yielding 0.49 g >80%) of 11 as colourless needles,
mp: 488C; IR >KBr): 2960, 1730, 1645, 1620 cm21 >CvO);
1H NMR >CDCl3): 1.32 >s, t-Bu), 1.44 >t, EtO), 3.87 >s,
MeO), 4.15 >q, EtO), 5.50>s, H±C vC); Anal. calcd for
C13H18O5: C, 61.40; H, 7.13; Found: C, 61.53; H, 7.25.
4.2.4. N,N0-Bis03-nitrophenyl)-urea 05).29 0.4 g of 4a were
heated for 2 h at 1708C in a round-bottomed ¯ask, ®tted with
a CaCl2-tube. After cooling down to rt the residue was tri-
turated with ether and the mixture was stirred at rt for 1 h.
The precipitate is ®ltered by suction and recrystallized from
methanol yielding 90mg >25%) of the urea 530 as a light
brown powder, mp 2458C >Ref. 30: 2488C); IR >KBr): 3365
>H±N), 1685 >CvO), 1600 cm21 >Aromat); 1H NMR
>DMSO-d6): 7.60, 7.82, 8.60 >m, Aromat), 9.40>s, H±N);
Anal. calcd for C13H10N4O5: C, 51.66; H, 3.31; N, 18.53;
Found: C, 51.59; H, 3.23; N, 18.44.
4.2.5. 1,1-Bis 0p-toluidylcarbonyl)-3,3-dimethyl-butan-2-
one 06). >a) 0.35 g of 4b were re¯uxed in 20ml xylene for
3 h. Then the solution was evaporated until the product
started to precipitate. The reaction mixture was cooled
over night in the refrigerator and then ®ltered by suction.
The crude product is washed with cold hexane, yielding
0.10 g >23%) of 6 as a brownish powder, identi®ed by
comparison with the product obtained under >b). >b) 0.5 g
of 4b were heated for 2 h at 1708C in a round-bottomed
¯ask, ®tted with a CaCl2-tube. After cooling down to rt
the residue was triturated with ether and the mixture was
stirred at rt for 1 h. The precipitate is then ®ltered by suction
and recrystallized from methanol to give 0.20 g >32%) of 6
as small bright beige platelets, mp: 1998C; IR >KBr): 3285
4.2.9. 6-t-Butyl-3-isopropyl-2-isopropylimino-5-methoxy-
carbonyl-oxazin-4-one 012). 0.35 g of 2 were added to a
solution of 0.30 g of diisopropylcarbodiimide in a small
amount of acetonitrile. The ¯ask was ®tted with a CaCl2-
tube and the mixture was stirred over night. The solvent was
evaporated at 508C affording a highly viscose orange oil
which crystallized partly at rt. The crude mixture was
dissolved in a minimum amount of dry ether and allowed
to vaporize slowly to give large, colourless crystals, washed
with small amounts of ice-cold pentane and sucked off
strongly yielding 0.31 mg >53%) of 12, mp: 678C; IR
>KBr): 2965, 1740, 1700, 1660, 1635 cm21 1H NMR
;
21
1
>H±N), 2980>CH), 1715, 1660, 1615 cm
>CvO); H
>CDCl3): 1.20>s, t-Bu), 1.25 >d, CH3±CH), 1.42 >d,
CH3CH±Nv), 3.83 >s, MeO), 4.10, 4.43 >m, HC±N); 13C
NMR >CDCl3): 18.6, 24.1 >CH3±CH), 27.5 >C>CH3)3), 37.5
>C>CH3)3), 46.0, 47.1 >CH3±CH), 52.8 >CH3O), 107.5
>CvC), 138.4 >CvN), 159.9 >CvC±O), 165.2 >O±
CvO), 167.9 >CvO); Anal. calcd for C16H26N2O4:
C, 61.92; H, 8.44; N, 9.10; Found: C, 61.87; H, 8.57; N,
9.02.
NMR >DMSO-d6): 1.23 >s, t-Bu), 2.30>t, H3C±Ph), 5.27
>s, H±C), 7.15, 7.40>m, Aromat), 9.22 >s, H±N); Anal.
calcd for C22H26N2O3: C, 72.11; H, 7.15; N, 7.64; Found:
C, 72.03; H, 7.19; N, 7.60.
4.2.6. 6-t-Butyl-2,3-diphenyl-5-methoxycarbonyl-oxazin-
4-one 08). 0.2 g of 2 were added to a solution of 0.2 g of
N-benzylidenaniline in acetonitrile under N2-atmosphere
and stirred at rt over night. The solvent is evaporated and
the remaining yellow oil was puri®ed by dry ¯ash chroma-
tography >DCFC), using hexane/ethylacetate 3:1 as an
eluent. The obtained light yellow oil was triturated with
cold hexane and the precipitated solid was ®ltered by
suction. Recrystallization from n-hexane yielded 0.2 g
>51%) of 8 as ®ne, colourless crystals, mp: 1028C; IR
>KBr): 2960, 1740 >Ester), 1665 >CvO), 1615 cm21
4.2.10. 6,6-Diphenyl-2-methoxy-3-pivaloyl-5-p-tolylimino-
pyran-4-on 014). 0.34 g of 2 were added to a solution of
0.52 g of N-4-tolyl-diphenylketenimine in dry diethylether
and the mixture was stirred over night. The obtained pre-
cipitate was ®ltered off by suction, washed with cold
pentane and dried, yielding 0.25 g >29%) of 14 as a white
powder, mp: 1438C; IR >KBr): 2960, 1705, 1670, 1640
1
>CvO), 1610cm 21 >Aromat); H NMR >CDCl3): 1.28 >s,
1
>Aromat); H NMR>CDCl3): 1.10>s, t-Bu), 3.82 >s, MeO),
t-But), 2.15 >s, CH3±Ph), 3.65 >s, MeO), 6.85, 7.05, 7.30 >m,
Aromat); 13C NMR >CDCl3): 26.0±27.6 >C>CH3)3), 54.1
>C>CH3)3), 55.8 >C>Ph)2), 57.4 >CH3O), 59.1 >CH3-Ph),
92.4 >s, CvC), 117.0> CvN), 125.5±142.0>m, Aromat),
161.3 >s, CvO), 162.8 >q, CvC±O), 206.9 >s, t-But-CvO);
Anal. calcd for C30H29NO4: C, 77.07; H, 6.48; N, 2.97;
Found: C, 76.81; H, 6.25; N, 2.99.
6.58 >s, H±C), 7.20, 7.45 >m, Aromat); Anal. calcd for
C22H23NO4: C, 72.31; H, 6.34; N, 3.83; Found: C, 72.17;
H, 6.44; N, 3.84.
4.2.7. 2-t-Butyl-3-methoxycarbonyl-pyran-4-one 010).
1.00 g of 2 were admixed with 0.4 g of ethylvinylether