Stereochemical Studies, 106. – Saturated Heterocycles, 110 Synthesis of Methylene‐bridged Partially Saturated Quinazolones

Abstract

Abstract 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(3 H )‐pyrimidinones ( 21 ).