Convenient Synthesis of Ethyl 4-Aryl-6-(trifluoromethyl)-2-oxo-2H-pyran-3-carboxylates and 4-Aryl-6-(trifluoromethyl)-2H-pyran-2-ones: Novel Highly Reactive CF₃-Containing Building Blocks

Abstract

An expedient synthesis of a series of 2-pyrones, bearing a CF 3 group at the 6-position and aryl group at position 4, from readily available aryl-4,4,4-trifluorobutane-1,3-diones, PCl 5, and sodium diethyl malonate is described.

Recent Advances in the Synthesis of 2-Pyrones

“…Usachev and co-workers developed a convenient synthesis of a series of 2-pyrones with a CF 3 group at the 6-position and aryl group at position 4, from readily available aryl-4,4,4-trifluorobutane-1,3-diones ( 125 ), PCl 5 , and sodium diethyl malonate ( 126 ) ( Scheme 37 ) [ 56 ].…”

Sulfur analogs of fluorinated pyrones, chromones and coumarins

“…While trifluoromethylated α-and γ -pyrones have been extensively investigated regarding their synthesis and chemical properties (1)(2)(3)(4)(5)(6), little attention has been paid toward the reactivity of their sulfur analogs, probably owing to the lack of general methods for the preparation of these compounds. Only a handful of papers describing some fluorine-containing thiopyrones are present in the literature.…”

Chemistry of fluoro-substituted β-diketones and their derivatives

“…199 However, in the similar reaction in dichloromethane, alkyl isocyanide attacks first the b-carbon atom of the diketone to form imino oxirane 131, which undergoes the Cope ± Claisen rearrangement to the corresponding unsaturated lactam 132. 200 A series of diverse heterocyclic compounds was obtained from trifluoromethyl-substituted diketones 21, namely: derivatives of 1H-pyrrole 133 ± 135, 201, 202 2-pyrone 136 203 and g-lactone 137. 204 Thus 1,2-diazabuta-1,3-dienes react regioselectively with 1,3-diketones 21 to form stable derivatives of 2-hydroxy-2-trifluoromethyl-2,3-dihydro-1H-pyrrole 133, the yield of by-products 134 being only 4% ± 6%; in the case of hetaryl-substituted diketones 21, the reaction is regiospecific.…”

“…202 The treatment of aryl-1,3-diketone 21 with phosphorus pentachloride followed by the introduction of sodium diethyl malonate into the reaction mixture afforded the corresponding 2H-pyran-2-ones 136 in moderate yields. 203 The reaction rate depended strongly on the nature of aryl substituent. Electron-donating substituents in the paraposition of the aromatic ring accelerate the process substantially, whereas electron-withdrawing substituents slow it down.…”