p-Toluenesulfonic acid → 1,5-Dioxa-8-azaspiro[5.4]decane benzyl carbamate

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Reaction Steps

Into a round bottom flask were placed 2.00 g (9.1 mmol) of 3-pyrrolidinone benzyl carbamate, from Example 1 Step 2, dissolved in 40 mL of toluene, 1.65 mL (22.8 mmol) of 1,3-propanediol and 0.09 g (0.46 mmol) of p-toluenesulfonic acid. The mixture was heated at 110°-125° C. for 48 hours. The solution was poured into 100 mL of 5% sodium bicarbonate solution, and the product was extracted into ethyl acetate, which was then dried over anhydrous sodium sulfate. The solvent was removed under vacuum, and the residue distilled in a kugelrohr apparatus (200° C. @ 2.5 Torr) to afford the title compound, MS: M/Z 295 (M+NH4), which was taken directly to the next step.

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