Synthetic Studies on Wedeligenin: Preparation of 3-Hydroxy-Substituted Decalincarbonitriles as a Model for 'A Ring' Annulation

Abstract

Six new 3-hydroxydecalincarbonitriles were synthesized by employing an annulation strategy involving intramolecular alkylation of 5-bromoalkyl substituted malononitriles or acetonitriles. 2-Allyl-2-methylcyclohexanone was condensed with malononitrile to give the dialkylcyclohexylidenepropanedinitrile (14). Alternatively, Horner-Emmons- Wittig condensation of the same ketone with diethyl cyanomethylphosphonate gave the corresponding acetonitrile (28). Reduction of the dinitrile with sodium borohydride to give a mixture of cis and trans cyclohexyl malononitriles followed by epoxidation of the allyl substituent, gave a separable mixture of four epoxides, two of which, (17) and (19), were site-selectively ring-opened to the bromohydrins. Each bromohydrin was quantitatively converted into its respective O- trimethylsilyl bromohydrin ether and cyclized to afford the respective decalindicarbonitriles (6) and (7). The substituted acetonitrile (28) was reduced to a 5 : 2 mixture of the corresponding cyclohexylacetonitriles with magnesium in methanol and the products were carried through to their respective O- trimethylsilyl bromohydrin ethers and cyclized to afford decalincarbonitriles (8)-(11).

The structure and stereochemistry of the new decalins were assigned by ¹H and ¹³C n.m.r. spectroscopy.