ORDER
REPRINTS
Synthesis of b-Keto Esters
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Typical Experimental Procedure for the Condensation of
Diazoacetates with Aldehydes
A solution of aldehyde (5.0 mmol) and diazoacetate (7.5 mmol) in
dichloroethane (10 mL) containing yttria-zirconia based Lewis acid catalyst
(50 mg; 10% w/w) was refluxed for the indicated length of time (Table 1)
under N2 atmosphere. The catalyst was recovered by filtration and solvent was
evaporated under reduced pressure to furnish the crude material. Purification
by silica gel column chromatography using pet ether: ethylacetate (9.8 : 0.2)
afforded the pure product.
4-Methyl-3-oxopentanoic acid methyl ester (3a): Colorless liquid.
IRnmax/cm21 (Neat): 1732, 1695, 1456. 1H NMR (CDCl3) d: 1.3
(d, J ¼ 6.25 Hz, 6H), 2.1–2.28 (m, 1H), 3.5 (s, 2H), 3.9 (s, 3H). 13C NMR
(CDCl3) d: 16.2, 33.5, 42.1, 50.0, 171.3, 196.0. Anal. calcd. for C7H12O3: C
58.32, H 8.39%; found: C 58.05, H 8.10%.
3-Oxo-3-phenylpropionic acid methyl ester (3b):[11] Colorless liquid.
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IRnmax/cm21 (Neat): 1735, 1695,1450. H NMR (CDCl3) d: [4.0,5.7,12.3]
(s, 2H), 4.1 (s, 3H), 7.8–7.4 (m, 3H), 8.1–7.9 (m, 2H).
3-(3-Nitrophenyl)-3-oxopropionic acid methyl ester (3c): White solid:
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M.P. 708C. IRnmax/cm21 (Neat): 3310, 1740, 1700, 1595, 1540. H NMR
(CDCl3) d: [3.9,5.8,12.6] (s, 2H), 4.1(s, 3H), 7.6–7.3 (m, 2H), 8.1–7.9
(m, 2H). 13C NMR (CDCl3) d: 42.2, 50.0, 89.0 (enolic), 123.5, 128.0, 129.5,
134.5, 138.3, 148.3, 171.0, 196.5. Anal. calcd. for C10H9NO5: C 53.82, H 4.06,
N 6.28%; found: C 53.50, H 3.80, N 5.91%.
3-(4-Methoxyphenyl)-3-oxopropionic acid methyl ester (3d): Color-
less liquid. IRnmax/cm21 (Neat): 3300, 1725, 1695,1590. 1H NMR (CDCl3) d:
3.7 (s, 3H) 3.8 (s, 3H), [4.1,5.5,12.6] (s, 2H), 7.8–6.9 (m, 4H). 13C NMR
(CDCl3) d: 42.1, 50.1, 56.2, 114.0, 129.7, 166.5, 171.5, 196.5. Anal. calcd. for
C11H12O4: C 63.45, H 5.81%; found: C 63.01, H 5.51%.
3-(3,4-Methylenedioxyphenyl)-3-oxopropionic acid methyl ester (3e):
1
Colorless liquid. IRnmax/cm21 (Neat): 3300, 1727, 1698, 1593. H NMR
(CDCl3) d: [4.0, 5.6, 12.6] (s, 2H), 4.1(s, 3H), 6.05 (s, 2H), 6.95 (d, J ¼ 7 Hz,
1H), 7.45 (d, J ¼ 7 Hz, 1H), 7.6–7.55 (m, 1H). 13C NMR (CDCl3) d: 42.1,
50.1, 91.3, 115.2, 121.5, 131.0, 147.5, 152.0, 171.0, 196.5. Anal. calcd. for
C11H10O5: C 59.46, H 4.54%; found: C 59.21, H 4.24%.
3-(2-Nitro-4-methylphenyl)-3-oxopropionic acid methyl ester (3f):
White solid: M.P. 1108C. IRnmax/cm21 (Neat): 3300, 1746, 1698, 1557, 1447.
1H NMR (CDCl3) d: 2.6 (s, 3H), [3.9, 5.7, 12.3] (s, 2H), 4.1 (s, 3H), 7.2 (s, 1H),
8.0 (d, J ¼ 7 Hz, 1H), 8.4 (d, J ¼ 7 Hz, 1H). 13C NMR (CDCl3) d: 19.9, 41.2,
50.1, 124.2, 129.3, 129.5, 135.5, 143.0, 171.0, 196.5. Anal. calcd. for
C11H11NO5: C 55.70, H 4.67, N 5.90% found: C 55.25, H 4.35, N 5.55%.