A short synthesis of (±)-laurene: mechanistic reinvestigation in palladium-catalyzed cycloreductions of 1,6-enynes

Two palladium-catalyzed cycloreduction strategies have been applied for the synthesis of laurene. Palladium-catalyzed cyclizations of 1,6-enynes initially form the corresponding alkylpalladium intermediates. While triethylsilane could directly reduce the intermediates to lead to the corresponding cycloreduced products, the intermediates in the presence of even excess formic acid underwent β-elimination to yield the dienes that were further reduced at the less hindered olefins to yield the cycloreduced products.