A facile synthesis of fused spiroketal skeleton:: 2,2′-spirobi(4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrochroman)

A one-pot synthesis of fused spiroketal skeleton, 2,2'-spirobi(4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrochroman) 4a-c, has been achieved for the first time by an application of Michael reaction between dimedone (5,5-dimethyleyclohexan-1,3-dione) 1 and trans, trans-diarylideneacetone (1,5-diaryl-1,4-pentadien-3-one) 2 using anhydrous ZnCl2 as catalyst. The spiroketalization was achieved efficiently via intramolecular cyclization of the Michael 1:2 adduct. (c) 2005 Published by Elsevier Ltd.