Spiro undecane group

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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