With imidates, esters (5–8) of di‐endo (1 and 2) and di‐exo (3 and 4) norbornane‐ and norbornene‐ß‐amino acids yield methylene‐bridged tetrahydro‐ (18 and 20) and hexahydro‐4‐quinazolinones (17 and 19); the reaction of the corresponding carboxamides (9–12) with 4‐chlorobenzaldehyde furnish hexahydro‐ (14 and 16) and octahydro‐4‐quinazolinones (13 and 15). The tetrahydro derivatives 18a, b can be selectively reduced to the hexahydro (17a, b) or octahydro (13b) compounds. The reaction with aldehyde is stereospecific; only the isomers containing the 2‐H and 8a‐H atoms in identical steric positions are formed. When boiled in a solvent or heated to melting, the 4‐quinazolines having a double bond in the carbobicycle split off cyclopentadiene with formation of the 2‐substituted 4(3H)‐pyrimidinones (21).
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