REACTIONS OF EPOXIDES OF 5-NORBORNENE-2,3-DICARBOXIMIDES . A CONCERTED, REDUCTIVE CLEAVAGE OF IMIDE RING BY LITHIUM ALUMINUM HYDRIDE

Both N-phenethyl-exo-5,6-epoxynorbornane-endo-2,3-dicarboximide (1c) and its exo-dicarboximide isomer (4) are stable to vigorous acid treatment. The stability of these norbornene epoxide systems under acid conditions is interpreted in terms of the electron-withdrawing effect of the carbonyl groups inhibiting carbonium ion formation, coupled with steric hindrance of the norbornyl system to intermolecular, backside nucleophilic attack. The epoxide function of these systems is also stable to intermolecular attack under basic conditions. Intramolecular opening of the epoxide ring by appropriately situated nucleophiles can, of course, occur with facility, and peracetic acid epoxidation of endo-3-(N-phenethylcarbamyl)-5-norbornene-erodo-2-carboxylic acid (12) proceeds with accompanying attack on the formed (or forming) epoxide function and formation of diol derivatives. Lithium aluminum hydride reduction of N-phenethyl-5-norbornene-exo- or endo-2,3-dicarboximide gives the expected 4,7-methanohexahydroisoindole (5 or 3, respectively). Reduction of 12 also yields 3 in a reductive alkylation process. Lithium aluminum hydride reduction of 4 affords 2-phenethyl-exo-5,6-epoxy-exo-4,7-methanooctahydroisoindole (6) retaining the oxirane ring. On the other hand, treatment of lc with lithium aluminum hydride yields N-phenethyl-endo-3-hydroxymethyl-exo-5-hydroxy-erado-2,6-methaniminonorbornane (9), formation of which requires reductive cleavage of both the imide and oxirane rings. 9 must arise via a concerted, intramolecular process with participation by the epoxide function. Analogs of 9 with other N substituents, and their mono- and diacyl derivatives have been prepared. Treatment of 6 with a small excess of ethereal hydrogen chloride in the cold gives the normal hydrochloride salt, but, when 6 is subjected to a larger excess of ethereal hydrogen chloride in the cold, the chlorohydrin IS is produced via a typical norbornyl carbonium ion rearrangement. This underlines the effect of the electron-withdrawing power of the carbonyl groups in stabilizing the norbornene epoxide system. © 1969, American Chemical Society. All rights reserved.