2,4-Dione, 3-substituted Knoevenagel reaction

Thiazolidinedione -triazole hybrids maybe synthesized by the one-pot reaction based on a Knoevenagel condensation followed by an alkyne-azide cycloaddition, between thiazolidine-2,4-dione, substituted aryl aldehydes, propargyl bromide, and substituted aryl azides using piperidine. The catalytic system is composed of CuS04 5H20 and sodium ascorbate in PEG-400 [119]. 

Hydrogenation of Knoevenagel products of 2,4-alkanediones over Raney nickel provides a simple route to 3-substituted 2.4-diones. Alternatively, reductive deacetylation can be accomplished using tetracarbonylhydridoferrate(0) in ethanol to prepare alkyl ketones. If the reaction is carried out in THF or acetone, exclusive reduction of the a,p-unsaturated double bond is observed. - Reactions of aldehydes with cyclic 1,3-diketones generally lead to the formation of Michael adducts under standard conditions. Indane-l,3-dione (103) yields Knoevenagel products with different aldehydes, ketones and ketimines, whereas perinaphthindane-l,3-dione (KM) gives the Michael adducts. ... 

On another occasion, Barbas s group developed the first organocatalytic diastereospecific and enantioselective direct asymmettic domino Knoevenagel/ Diels-Alder reactions that produce highly substituted spiro[5,5]undecane-l,5,9-triones 57 from commercially available 54, aldehydes 55, and 2,2-dimethyl-l,3-dioxane-4,6-dione 56 (Scheme 1.16) [18]. Among the catalysts screened, 5,5-dimethyl thiazolidinium-4-carboxylate (DMTC) proved to be the optimal catalyst with respect to yield, and provided 57 in 88% yield and 86% ee. Up to 93% yield and 99% ee were observed when the reaction was extended to other substrates. It is noteworthy that the product 57 was accompanied by a trace amount of the unexpected symmetric spirocyclic ketone 58. 

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