Assembly of trifluoromethylated fused tricyclic pyrazoles via cyclization of β-amino cyclic ketones

Abstract

Fused polycyclic pyrazoles are an important type of heterocyclic compounds, thus, the development of efficient methods for their preparation becomes highly urgent. Herein, we reported an efficient method for the...

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

“…According to the above experimental results and literature reports [ 39 – 41 58 – 59 ], a possible mechanism for this Cu-catalyzed reaction of β-trifluoromethyl β-amino esters was proposed in Scheme 4 . Initially, β-trifluoromethyl β-amino ester 1a reacts with tert -butyl nitrite to form trifluoromethylated β-carbonyl diazo intermediate A .…”

“…Due to the instability of β-carbonyl diazo compounds and the occurrence of possible side reactions [58][59][60][61], screening of reaction conditions to optimize this conversion and inhibit the occurrence of side reactions was carried out with benzyl 3-amino-4,4,4-trifluorobutanoate (1a) and benzoic acid (3a) as model substrates. The initial reaction of amine 1a and acid 3a in acetonitrile in the presence of diazotization reagent tert-butyl nitrite with CuI (10 mol %) as catalysts for 2.5 h at room temperature proceeded to afford the desired unsymmetrical β-trifluoromethyl diacyl-β-amino ester 4a in 54% yield (Table 1, entry 1).…”