Di-tert-butyl dicarbonate → 3a,4,7,7a-Tetrahydro-2-hydroxy-4,7-methano-1H-isoindole-1,3(2H)-dione

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Reaction Steps

endo-N-Hydroxy-5-norbornene-2,3-dicarboximide (NBD) (3.59 g, 20 mmol) is dissolved in absolute ethanol (100 mL), and is then evaporated to dryness in vacuo to remove the residual moisture from the reagent. The residue is redissolved in freshly prepared absolute ethanol (60 mL), and thallous ethoxide (1.42 mL, 20 mmol) is added dropwise with vigorous stirring. The solution is stirred for 3 h at room temperature and then overnight at 4° C. The white precipitate which forms in the course of the reaction is collected by filtration, washed with cold ethanol, and dried under high vacuum. The solid material is suspended in methylene chloride (100 mL), and di-tert-butyl dicarbonate (4.37 g, 20 mmol) is added dropwise. The solution is stirred overnight at room temperature and is then washed with water (2×10 mL). The organic layer is dried over anhydrous MgSO4, filtered, and evaporated to dryness to give the crude product as a white solid. The solid is suspended, with vigorous stirring, in anhydrous ether (60 mL) for 2 h, followed by filtration, to give 3.0 g of the pure product. Upon storage of the filtrate at −20° C. overnight, additional pure product precipitates giving a total of 3.63 g of the title compound in two crops in an overall yield of 65%.

Provenance & Evidence