Synthesis and acid-catalysed rearrangement of (1R,2R,5S,6S)-Tricyclo[4.3.1.1]undecane

Abstract

(1R,2R,5S,6S)-Tricyclo[4.3.1.1^2,5]undecane (II) was synthesised by hydride transfer reduction–ring expansion of (1RS,2RS,6RS,7SR)-2-hydroxymethyltricyclo[5.2.1.0^2,6]decane (I) with sulphuric acid and n-pentane. The (1RS,2SR,6SR,7SR)-isomer (VIII) of (I) did not undergo ring expansion, but gave a simple reduction product, i.e. the 2-methyl derivative (X). Further isomerisation of the tricycloundecane (II) gave (1RS,2RS,6SR,7SR)-2-methyltricyclo[5.2.1.0^2,6]decane (X) and its (1RS,2SR,6RS,7SR)-isomer, (XI), tricyclo[5.3.1.0^3,8]undecane (XII), tricyclo[5.3.1.0^2,6]undecane (V), and 2-methyladamantane. The 2-methyltricyclodecanes (X) and (XI) were isomerised quantitatively to methyladamantanes in the presence of aluminium chloride.