A comparative study using conventional methods, ionic liquids, microwave irradiation and combinations thereof for the synthesis of 5-trifluoroacetyl-1,2,3,4-tetrahydropyridines

Haloacetylated Enol Ethers: a Way Out for the Regioselective Synthesis of Biologically Active Heterocycles

“…For comparison purposes, Scheme 18 shows the reactions of cyclic enones 4 with primary amines in the absence and presence of the alkoxy moiety neighboring the oxygen of the pyran ring. When the alkoxy group is absent, the corresponding α‐substituted β‐enaminone 63 is obtained, [89] and when present, the aldehyde moiety of 64 is rapidly transformed into the corresponding imine 65 , which spontaneously makes an intramolecular nucleophilic attack on the secondary amine, and, as a result, 1,2,3,4‐tetrahydropyridine motifs are obtained [90–94] . Given that several methods involving catalysts to prepare tetrahydropyridines using parent substrates have been reported, [95–98] the high reactivity of the push‐pull system on these fluorinated β‐enaminones 65 may be the main cause for the spontaneous cyclization observed.…”

Design, Synthesis, and Cholinesterase Inhibitory Activity of 4‐Substituted‐6‐(trihalomethyl)‐2‐methylsulfanyl Pyrimidines

“…Besides this, the introduction of a À CF 3 group into heterocycles can greatly influence both biological and chemical properties, due to the unique characteristics (e. g., lipophilicity, bioavailability, and metabolic stability) of the trifluoromethyl group. [9,10] β-Alkoxyvinyl trihalomethyl ketones have proven to be successful as CCC-building blocks in the regioselective synthesis of several heterocyclic scaffolds [11][12][13] (including pyrimidine rings), easily allowing the introduction of trihalomethyl groups. [14,15] On the other hand, allylic brominated β-alkoxyvinyl trihalomethyl ketones (enones) have been far less explored in heterocyclic synthesis, especially in regard to pyrimidines.…”

“…β‐Alkoxyvinyl trihalomethyl ketones have proven to be successful as CCC ‐building blocks in the regioselective synthesis of several heterocyclic scaffolds [11–13] (including pyrimidine rings), easily allowing the introduction of trihalomethyl groups [14,15] . On the other hand, allylic brominated β‐alkoxyvinyl trihalomethyl ketones (enones) have been far less explored in heterocyclic synthesis, especially in regard to pyrimidines [16] .…”

The Wonderful World of β‐Enamino Diketones Chemistry

“…Speaking in terms of reactivity toward a nitrogen nucleophile (e.g., hydrazine or amines), according to reports in the literature for parent structures, the 1,4‐conjugated addition is expected to occur first, followed by nucleophilic addition at the carbonyl carbon. [ 27–31 ] This may become an issue when dealing with the 1,3‐diketone, given that there are two carbonyls that may experience the addition, which could furnish a mixture of two products (Scheme 3).…”