Rearrangements in the monoterpene series (1968)
AuthorsDansted, Erikshow all
The stereochemistry of a number of (2,3)-, (2,10)- and (2,3,10)- substituted pinanes has been established. Hydroxylation of α-pinene with permanganate gave 10β-pinane-2,3α-diol, similar treatment of β-pinene gave 10β-pinane-2,10-diol. 2,10-Epoxy-10β-pinane was formed by reaction of nopinone with dimethyl sulphonium methylide. Some reactions of substituted pinanes involving carbonium ion formation at C2 have been studied. The path of rearrangement of these compounds depends on the conformation of the intermediate carbonium ion; an 'up' conformation leads to C1-C7 bond shift or rupture, whereas a 'down' conformation leads to C1-C6 bond shift or rupture. Reaction of β-pinene with mercuric acetate gave dimeric hydrocarbons. The NMR spectra of a number of pinanes have been recorded. 2,10-Epoxy-10β-pinan-3α-ol and 2,10-epoxy-10β-pinan-3β-ol reacted with aqueous alkali to give pinocarvone. The reaction was first order in epoxide and hydroxyl ion, the 3β-hydroxy-epoxide reacting faster than the 3α-hydroxy-epoxide.