The synthesis of Tetracyclo[5,3,1,0^3,5,0^4,9]undecan-2-one and the acid-catalysed and reductive cleavages of the cyclopropyl ring

Abstract

Tetracyclo[5,3,1,0^3,5,0^4,9]undecan-2-one (2,4-dehydro-5-homoadamantanone) (3) was synthesized by copper-catalysed intramolecular insertion of a diazoketone into a double bond. Acid-catalysed opening of the cyclopropyl ring in aqueous acetic acid cleaved the C3-C4 bond to give a mixture of exo-7-hydroxytricyclo[4,3,1,1^3,8]undecan-4-one (13) and its acetate (12). Under the same conditions except for the presence of bromide ion, a mixture of (12), (13) and exo-7- bromotricyclo[4,3,1,1^3,8]-undecan-4-one (17) was obtained. Reduction of (17) with LiAlH₄ gave homoadamantanol. Reduction of (3) with lithium in liquid ammonia gave cleavage of the C 3-C 5 bond to afford tricyclo[5,3,1,0^4,9]-undecan-2-one (4), the structure of which was confirmed by independent synthesis.