Compound 2b (0.1 g, 0.47 mmol) was dissolved in chloroform (5 ml) and triphenylphosphine (0.13 g, 0.49 mmol) was added. The reaction mixture was stirred and the progress of the reaction was monitored by TLC until complete disappearance of the peroxide (reaction time about 10-20 min). Subsequently, p-toluenesulfonic acid (9 mg, 0.05 mmol) was added and the reaction mixture was heated to 50 °C. After 4 hours of reaction, the mixture was concentrated to dryness under reduced pressure and purified directly by column chromatography to afford the target compound 7,9-di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione (0.074 g, 87% yield). The product characterization data were as follows: IR (neat, cm-1): 2957, 1774, 1647; 1H NMR (500 MHz, CDCl3): δ6.51 (s, 2H), 2.77 (t, J=8.3 Hz, 2H), 2.28 (t, J=8.3 Hz, 2H), 1.23 (s, 18H); 13C NMR ( 125 MHz, CDCl3): δ 185.5, 175.8, 147.7, 137.1, 79.9, 34.9, 33.3, 29.3, 28.6; HRMS (ESI) calculated value of C17H24O3Na [M+Na]+: 299.161762, measured value: 299.161663.
![7,9-ditert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione](/CAS/20180703/GIF/82304-66-3.gif)