Convenient one-pot MCRs to trifluoromethylated spiropiperidine under catalyst-free conditions

One-pot, four-component reactions of 1,2-diphenylpyrazolidine-3,5-dione, ethyl 4,4,4-trifluoroacetoacetate, aromatic aldehyde and ammonium acetate afforded highly functionalized ethyl 8-hydroxy-1,4-dioxo-2,3,6,10-tetraphenyl-8-(trifluoromethyl)-2,3,7-triazaspiro[4.5]decane-9-carboxylate derivatives 5 in good yields. The most advantage of this reaction was the high diastereoselectivity because only one diastereoisomer 5 was produced. The effect of NH₄OAc and solvents on the reaction efficiency and yield was briefly investigated. Meanwhile, the further transformation of hemi-aminal moieties to the corresponding dehydrated product was also achieved under the mild reaction conditions. And a plausible reaction mechanism for the formation of products 5 was illustrated based on the control experiments.