Abstract
This paper describes the addition of a range of electrophiles to 1 . An unusual and unpredicted stereochemistry of addition has been observed in line with our original photochemical observations.
Key words
electrophilic attack - photochemical addition - kainates - oxazolidinone -
ab initio calculations - molecular modelling
References
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Typical Experimental Procedure :
[11 (5
R
,6
S
,7
R
)-1-aza-3-oxa-6,7-epoxybicyclo[3,3,
O
]-octan-2-one (
6)
.
To a stirred solution of oxazolidinone 1 (4.00 g, 32 mmol) in dimethoxymethane (130 mL) and MeCN (260 mL) were added tetrabutylammonium hydrogen sulfate (0.43 g, 1.28 mmol), acetone (71 mL, 960 mmol) and K2 CO3 (0.1 M in water, 64 mL). A solution of EDTA (4 × 10-4 M in water, 341 mL) acidified with enough HOAc to dissolve the insoluble solid was added to oxone® (78.7 g, 992 mmol). The resulting solution and a solution of K2 CO3 (87.2 g, 631.5 mmol) in water (341 mL) were concomitantly added to the initial solution of oxazoline 1 over 5 h. The reaction mixture was then extracted with EtOAc (3 × 100 mL) and washed with brine (100 mL) and water (100 mL). The combined organic extracts were dried over MgSO4 and concentrated under reduced pressure. The resulting oil was purified by flash column chromatography (60% EtOAc-petroleum ether) to give epoxide 6 as a white crystalline solid (3.60 g, 80%); mp (uncorrected) 60-63 °C; [α]23
D -8.6 (c = 1.91, CHCl3 ). IR (film): 3059, 2922, 1748 (s), 1410 (s), 1199, 1075 (s) cm-1 . 1 H NMR (500 MHz, C6 D6 ): δ = 3.95 (dd, J = 8.7, 3.6 Hz, 1 H), 3.87 (apparent t, J = 8.7 Hz, 1 H), 3.80 (d, J = 13.2 Hz, 1 H), 3.08 (dd, J = 8.7, 3.6 Hz, 1 H), 2.97 (d, J = 2.8 Hz, 1 H), 2.91 (d, J = 2.8 Hz, 1 H), 2.50 (d, J = 13.2 Hz, 1 H). 13 C NMR (75 MHz, CDCl3 ): δ = 163.2, 64.5, 58.4, 55.7, 55.5, 48.9. HRMS: m /z [M+ ] calcd for C6 H7 NO3 : 141.0426; found: 141.0420.
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