An Improved Synthesis of 2,2-Dialkyl-1,3-Indanediones

2,2-Dialkyl-1,3-indanediones are useful synthetic intermediates (^1,2) and are know to possess an anticonvulsive activity (³). These compounds are usually prepared by alkylation of 1,3-indanedione under drastic conditions and thus are obtained with low yields (20% to 40%). We describe here a convenient and high yield procedure for the synthesis of symmetrical and unsymmetrical 2,2-dialkyl-1,3-in-danediones based on alkylation of 1,3-indanediones in the presence of celite coated with potassium fluoride (KF-celite). This new reagent has been very recently used to carry out various alkylation reactions (³). We found that KF-celite promotes excellent C-dialkylation (⁴) of 1,3-indanedione la, giving rise to symmetrical 2,2-dialkylated compounds 2a. In the same way, unsymmetrical 2,2-dialkyl-1,3 indanediones 2b can be easily prepared from 2-methyl-1,3-indanedione Ib (⁵).