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 hemiaminal 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. (C) 2018 Elsevier Ltd. All rights reserved.