Organic fluorine compounds. Part XXXIX. Reactions of α-fluoro-β-keto-esters

Abstract

Ethyl 2,4-difluoroacetoacetate, ethyl ethoxalylfluoroacetate and the analogous benzyl ester gave the normal Wittig reaction with triethyl phosphonoacetate, whilst ethyl formylfluoroacetate gave a dimer of diethyl 4-fluoroprop-1 -ene-l,3-dicarboxylate. Treatment of the sodio-enolate of ethyl formylfluoroacetate with acid chlorides gives 3-acyloxy-2-fluoroacrylates. The acyloxy-group of these compounds can be replaced easily by aromatic amines, and, furthermore, they can be employed for the synthesis of pyrimidines, e.g., 5~fluorouracil.

Palladium-Catalyzed Intermolecular Dehydrogenative Aminohalogenation of Alkenes under Molecular Oxygen: An Approach to Brominated Enamines

“…Herein we disclose the first example of a highly regio- and stereoselective Pd-catalyzed dehydrogenative aminohalogenation of activated alkenes with molecular oxygen as the sole oxidant (Scheme b) . The present protocol directly employs simple aromatic amines as the nitrogen sources and, more importantly, provides highly convenient access to a halogenated enamine scaffold which was difficult to prepare by traditional methodologies …”

A β-Fluoroamine Inhibitor of Purine Nucleoside Phosphorylase

“…(9, 27) We chose to initially pursue a synthesis of the racemate, with the required fluoropyrrolidine (±)− 11 (Scheme 1) to be constructed through a cycloaddition of azomethine ylid 6 to the known fluoroacrylate 7 . (28, 29)…”

“…(28) Z -configuration was assigned on the basis of the H−F coupling constant ( 3 J H,F = 18 Hz). (29, 37) Cycloaddition between ester 7 and the azomethine ylid 6 , generated in situ from N -methoxymethyl- N -(trimethylsilylmethyl)benzylamine ( 5 ), gave pyrroldine ester (±)− 8 in good yield.…”

“…9,27 We chose to initially pursue a synthesis of the racemate, with the required fluoropyrrolidine (()-11 (Scheme 1) to be constructed through a cycloaddition of azomethine ylid 6 to the known fluoroacrylate 7. 28,29 The 1,3-dipolar cycloaddition between azomethine ylids and alkenes is a potent method for the construction of substituted pyrrolidines with defined regio-and stereochemistry. Such a cycloaddition is the key step in one of the routes to diol 4, 30,31 and a plethora of other examples can be found in the literature.…”

“…DADMe-Immucillin-H ( 2 ) is most easily assembled by means of a three-component Mannich reaction between 9-deazahypoxanthine, formaldehyde, and pyrrolidine 4 . This method, which is tolerant of variations in both the amine and 9-deazapurine, has provided us with many variants of 2 and so was an obvious choice for our synthesis of 3 . , We chose to initially pursue a synthesis of the racemate, with the required fluoropyrrolidine (±)- 11 (Scheme ) to be constructed through a cycloaddition of azomethine ylid 6 to the known fluoroacrylate 7 . , …”