Alkanoyl halides

Perfluorophenyl)copper exhibits high reactivity towards organic substrates. and reacts with fluorinated or nonfluorinated aryl iodides (e.g., formation of 5), fluorinated vinyl iodides, al-kynyl bromides and iodides, allyl halides, alkanoyl halides, and iodomethane to afford the corresponding coupled products in good yields. (Perfluorophenyl)copper readily undergoes addition in a syn fashion to perfluorobut-2-yne to form a perfluorovinylcoppcr reagent 6, which can be quenched by electrophiles (e.g. formation of 7). Recall that (per-fluorophcnyl)coppcr reacts with (trifluoromethyl)copper to form (perfluorophenethyl)copper (Section 2.1.1.3.3.). 

Tetrafluoropyridyl organometallic reagents can be prepared by reaction of 4-bromotetra-fluoro- or tctrafluoro-4-iodopyridine with zinc or cadmium in dimethylformamide at room temperature.83 Metathesis of these reagents with copper(l) bromide affords the (2.3,5,6-tetra-fluoro-4-pyridyl)copper reagent. The latter species undergoes high-yield substitution reactions with allyl halides, vinyl iodides, aryl iodides, and alkanoyl halides. 

E.sters are the most prevalent carboxylic acid derivatives in nature. They also are convenient compounds for. synthetic purposes because their intermediate reactivity makes them easy to prepare and store for later use. Alkanoyl halides, in contrast, are so reactive toward water that it takes some care to prevent them from hydrolyzing to some extent upon extended storage. Esters are easily prepared and readily converted into many types of compounds by reactions at both their carbonyl and a-carbons (Chapter 23). 

No tricks here The mechanism is almost exactly as shown in Section 19-12, with only minor diflTerences. Because the method starts with an alka-noyl halide, step I is unnecessary. Step 2 (enolization) occurs as written. The third step u.ses CI2, generated in low concentration from NCS, or Br2, formed in the. same way from NBS, or I2. The fourth step in the mechanism doesn t apply because only alkanoyl halides are present, not carboxylic acids. 

Alkanoyl group RC O—. the fragment w ith common name acyl—as in the alkanoyl halides, carboxylic acid derivatives. 

Recall (Section 19-8) that carboxylic acids may react with alkanoyl halides to produce anhydrides. Upon conversion of one carboxylic acid function of a 1,4- or 1,5-diacid to a halide, the other acid function... 

Amides may be made directly from the acids, or indirectly via alkanoyl halides, anhydrides (less efficiently, because only one of the two alkanoyl groups is converted into an amide), or esters. Thus we have the following options ... 

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