Extension of β-chloroenals to ethyl 5-chloro-2,4-pentadienoates using Wadsworth–Emmons reactions: subsequent conversions to 5-aryl-5-chloro-2,4-pentadienoic acids and 5-aryl-2-penten-4-ynoic acids

Novel Synthesis, Reactivity, and Stereochemistry of Substituted 3-Trifluoromethyl- and 3-Perfluoroalkyl-3-phenoxyprop-2-enal

“…The Wadsworth−Emmons product is obtained, and the conjugated ester derivative 5 is isolated as a single stereoisomer in very high yields (>98%) (Scheme ). There has been interest in conjugated unsaturated systems, such as polyenes, as a consequence of the physiological behavior exhibited by representatives of these systems. 2c, They have also been shown in many cases to serve as effective synthons in the construction of a wide variety of interesting molecules, such as retinoid analogues …”

“…α,β-Unsaturated carbonyl derivatives substituted in the β-position with good leaving groups (chloro or alkoxy) serve as convenient building blocks for synthesis of different classes of acyclic, carbocyclic, and heterocyclic compounds. , In recent years, considerable attention has been given to the development of new procedures for the synthesis of fluorine-containing synthons, for example, trifluoromethylated β-chloroenones (ClCHC(Ar)COCF 3 and ClC(CF 3 )CHCOAr) 3,4 or the β-alkoxyvinyl trifluoromethyl ketones (ROCHCHCOCF 3 ). , Generally, nucleophiles attack the β-carbon atom with elimination of the alkoxy group , or chloride anion; , therefore, those enones are fluorinated keto aldehyde chemical analogues and are extensively used for the synthesis of various trifluoromethylated compounds which are often used in both medicine and agricultural chemistry. , …”