Reaktion #56020

Reaktionsgleichung

2-nitroethanethiol

4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemthyl)azetidin-2-one

4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one

crude product ( 13 )

Benzyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate

potassium carbonate

→

benzyl 3-(2-nitroethylthio)-7-oxo-1-azabicyclo[3.2.0]heptane-2-carboxylate

Lösungsmittel

ethyl acetate

dimethylformamide

dimethylformamide

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe residue was partitioned between ethyl acetate and brine
2. 2
   Sonstigethe organic phase was separated
3. 3
   Trocknendried over sodium sulphate
4. 4
   Einengenconcentrated
5. 5
   SonstigeIt was chromatographed on silica gel 60 (<230 mesh)
6. 6
   Wascheneluting with ethyl acetate/60°-80° petroleum ether 3:7 grading to 7:3, and fractions
7. 7
   workup.ADDITIONcontaining the required products
8. 8
   Sonstigewere rechromatographed on the same support
9. 9
   Sonstigeethyl acetate/60°-80° petroleum ether 4:6

Vorschrift

An ethyl acetate solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemthyl)azetidin-2-one (37) (1.46 g) was ozonolysed and cyclized as described in Example 53. The crude product (13) was dissolved in dry dimethylformamide (5 ml) and a solution of 2-nitroethanethiol (0.30 g) in dimethylformamide (2 ml) was added, followed by powdered potassium carbonate (0.19 g). The reaction was stirred at room temperature for 2 hours and the solvent was then stripped off under high vacuum. The residue was partitioned between ethyl acetate and brine and the organic phase was separated, dried over sodium sulphate and concentrated. It was chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 3:7 grading to 7:3, and fractions containing the required products were rechromatographed on the same support using ethyl acetate/60°-80° petroleum ether 4:6. This gave two isomers of benzyl 3-(2-nitroethylthio)-7-oxo-1-azabicyclo[3.2.0]heptane-2-carboxylate (122) and (123). The less polar compound was the 2α, 3α-isomer (122) (0.025 g); νmax (CHCl3) 3020, 2960, 1770, 1750sh and 1560 cm-1 ; τ(CDCl3) 2.66(5H, s, phenyl), 4.82(2H, s, benzyl CH2), 5.60(2H, t J7 Hz, CH2NO2), 5.65(2H, d, J61/2 Hz, C2-H), 5.9-6.4(2H, m, C3-H and C5-H), 6.70(1H, dd J15 and 41/2 Hz, C6-H), 6.94 and 6.96(2H, 2t J7 Hz, SCH2), 7.26(1H, dd J15 and 2 Hz, C6-H), 7.41(1H, dt J13 and 6 Hz, C4-H), and 8.44(1H, ddd J13, 9 and 7 Hz, C4-H); (M+ at m/e 350. C16H18N2O5S requires 350). The more polar product was the 2β, 3α-isomer (123) (0.010 g); νmax (CHCl3) 3000, 2940, 1770, 1740 and 1560 cm-1 ; τ(CDCl3) 2.65(5H, s, phenyl), 4.72 and 4.89 (2H, ABq J12 Hz, benzyl CH2) 5.64(2H, t J61/2 Hz, CH2NO2), 5.89(1H, d J7 Hz, C2-H), 6.1-6.5(2H, m, C3-H and C5-H), 6.7-7.1(3H, m, C6-H and SCH2 ), 7.18(1H, dd J15 and 21/2 Hz, C6-H), 7.73(1H, dt J12 and 6 Hz, C4-H) and 8.09(1H, td J12 and 10 Hz, C4-H); (M+ at m/e 350. C16H18N2O5S requires 350).

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