Cyclization into hydrindanones using samarium diiodide

Samarium(II) iodide has been employed to promote vinylogous pinacol couplin g reaction of aldehyde onto alpha,beta-unsaturated ketones. The diastereose lectivity of 6-endo products was changed by addition of a proton source and /or HMPA and by the reaction temperature. The cyclization reactions describ ed herein provide a general approach to the syntheses of 3,3-dimethylhydrin danes with a cis-relationship between the OH at C-4 and the proton at C-3a with good diastereoselectivity and under mild reaction conditions.