Bridgehead substitution reactions of 3-methoxy-4-azahomoadamantane via N-acyliminium ions. A novel route to some [3,4]-fused 4-azahomoadamantane heterocycles

Abstract

Treatment of 3-methoxy-4-methoxycarbonyl-(9) and 4-acetyl-3-methoxy-4-azahomoadamantane (10) with AlCl₃ in benzene afforded the corresponding 3-phenyl derivatives (12) and (17) accompanied by considerable amounts of the ring-opened products (13) and (18), respectively. The reaction of compound (9) with phenylethynyltrimethylsilane (2) and AlCl₃ gave the 3-phenylethynyl substitution product (19), while the same reaction of (10) gave the 3-phenylacetyl product (21). The cyclization of compound (19) with partially hydrated AlCl₃ afforded the oxazinone (23), the oxazolidinone (24), and the hydrochlorinated product (25); the base-catalysed cyclization of (21) gave the 3-pyrrolin-2-one (26). Intramolecular substitution of the 3-methoxy group with the aryl group of the arylureas (28a–c) took place smoothly with AlCl₃ to give the corresponding quinazolinones (29a–c) in good yields.