Efficient Synthesis and Antimicrobial Evaluation of New Organophosphorus Dioxaspirodecanone Derivatives

Claisen-Schmidt condensation reaction of 1,4-cyclohexanedione monoethylene ketal (1) with p-methoxybenzaldehyde, under base catalyzed conditions, has afforded 7,9 bis (4-methoxybenzylidene)-1,4-dioxaspiro[4,5]decan-8-one (2). The bisbenzylidene 2 was functionalized with some selected organophosphorus reagents. Thus, compound 2 was reacted with tris(dialkylamino) phosphines 3a,b, in refluxing toluene and in presence of a catalyst, to give a product mixture of the corresponding oxaphospholedioxolane oxides 8a,b and tetraalkylphosphonicdiamides 9a,b. Moreover, the reaction of bisbenzylidene 2 with the trialkylphosphite reagents 4a,b afforded the corresponding dialkylphosphonate derivatives 10a,b. The phosphonate 10b could be also obtained upon reacting bis-bezylidene 2 with diisopropylphosphite (5) under the same experimental conditions. The reaction of bis-benzylidene 2 with the stable phosphonium ylides, namely, (carbmethoxymethylene)- (6a) or (carbethoxymethylene) -triphenylphosphorane (6b) , afforded the dihydrospiroindenedioxolanone derivative 11 under the given reaction conditions. Moreover, compound 11 was also obtained from reaction of the dialklyphosphonoacetate Wittig-Horner reagents 7a,b with compound 2. On the other hand, reaction of diethyl(cyanomethylene) phosphonate 7c with bis-bezylidene 2, in an ethanolic sodium ethoxide solution, gave the 1,4dispiroylidene acetonitrile derivative 12. Possible reaction mechanisms are discussed and the structures of the new products are confirmed from their analytical and spectroscopic data. The antimicrobial activity of the synthesized compounds was also investigated.