Triethylamine → rel-(3aR,5R)-5-cyclopropyl-3,3a,4,5-tetrahydro-7H-pyrano[3,4-c][1,2]oxazole

An aqueous solution of sodium hypochlorite (6.15% solution, 27.1 mL, 22.4 mmol) was added drop-wise over 24 minutes to a solution of 2-[(1-cyclopropylbut-3-en-1-yl)oxy]-N-hydroxyethanimine (C51) (1.85 g, 10.9 mmol) and triethylamine (0.114 mL, 0.818 mmol) in dichloromethane (64 mL) that was immersed in a room temperature water bath. The rate of addition was adjusted to maintain the internal temperature of the reaction between 19.5° C. and 22.8° C. After completion of the addition, the reaction mixture was diluted with water (50 mL) and the aqueous layer was extracted with dichloromethane (3×50 mL). The combined organic layers were washed with saturated aqueous sodium chloride solution (50 mL), dried over sodium sulfate, filtered, and concentrated in vacuo (300 mbar, 40° C.) to provide the product as a pale yellow oil. The indicated relative stereochemistry of compound C52 was assigned based on nuclear Overhauser enhancement studies, which revealed an interaction between the methine protons on carbons 3a and 5. Yield: 1.73 g, 10.3 mmol, 94%. GCMS m/z 167 [M+]. 1H NMR (400 MHz, CDCl3) δ 4.73 (d, J=13.5 Hz, 1H), 4.61 (dd, J=10.2, 8.0 Hz, 1H), 4.14 (dd, J=13.5, 1.0 Hz, 1H), 3.80 (dd, J=11.5, 8.0 Hz, 1H), 3.36-3.48 (m, 1H), 2.83 (ddd, J=11.0, 8.0, 1.8 Hz, 1H), 2.31 (ddd, J=13.0, 6.5, 1.5 Hz, 1H), 1.64 (ddd, J=12.8, 11.4, 11.3 Hz, 1H), 0.89-0.98 (m, 1H), 0.51-0.64 (m, 2H), 0.38-0.45 (m, 1H), 0.21-0.28 (m, 1H).

1. customwas immersed in a room temperature
2. additionThe rate of addition
3. temperatureto maintain
4. customthe internal temperature of the reaction between 19.5° C. and 22.8° C
5. additionAfter completion of the addition
6. extractionthe aqueous layer was extracted with dichloromethane (3×50 mL)
7. washThe combined organic layers were washed with saturated aqueous sodium chloride solution (50 mL)
8. dry with materialdried over sodium sulfate
9. filtrationfiltered
10. concentrationconcentrated in vacuo (300 mbar, 40° C.)

ORD record

ord-8172bc04d3a24f86b8139b1fafdf4ec0

Source dataset

uspto-grants-2015_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09045498B2