Radical Cyclizations Leading to the Bicyclo[2.2.1]heptane Framework: A New Radical Approach to (±)-(Z)-β-Santalol

Abstract

Tandem radical cyclizations of acyclic iodides, including [3-(2-iodoethyl)-6,10-dimethyl-undeca-5,9-dien-1-ynyl]-dimethyl­phenylsilane lead in good yields to bicyclo[2.2.1]heptane derivatives. The cascade relies on two sequential radical-mediated 5-exo-cyclizations. The radical approach is illustrated with the total ­synthesis of racemic-(Z)-β-santalol. The results are remarkable, two fused rings and one stereogenic center are formed in a single operation. A new ‘coordinated’ hydride appeared to be useful in the ­cascade.

Key words

bicyclic compounds - domino reactions - hydrides - ­natural products - radicals

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