Acyl-halo-addition

Addition of Acyl Halides (Addition of Halogen, Carbon) Acyl-halo-addition... 

In addition to this, Grignard reagents prepared from alkyl and acyl halo-genides can be converted by reaction with dimethylformamide and 2,4-dinitrophenylhydrazine to 2,4-dinitrophenylhydrazones of aldehydes (see p. 218) (4). 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

Ion 21 can either lose a proton or combine with chloride ion. If it loses a proton, the product is an unsaturated ketone the mechanism is similar to the tetrahedral mechanism of Chapter 10, but with the charges reversed. If it combines with chloride, the product is a 3-halo ketone, which can be isolated, so that the result is addition to the double bond (see 15-45). On the other hand, the p-halo ketone may, under the conditions of the reaction, lose HCl to give the unsaturated ketone, this time by an addition-elimination mechanism. In the case of unsymmetrical alkenes, the attacking ion prefers the position at which there are more hydrogens, following Markovnikov s rule (p. 984). Anhydrides and carboxylic acids (the latter with a proton acid such as anhydrous HF, H2SO4, or polyphosphoric acid as a catalyst) are sometimes used instead of acyl halides. With some substrates and catalysts double-bond migrations are occasionally encountered so that, for example, when 1 -methylcyclohexene was acylated with acetic anhydride and zinc chloride, the major product was 6-acetyl-1-methylcyclohexene. ... 

Similar additions have been successfully carried out with carboxylic acids, anhydrides, acyl halides, carboxylic esters, nitriles, and other types of compounds. These reactions are not successful when the alkene contains electron-withdrawing groups such as halo or carbonyl groups. A free-radical initiator is required, usually peroxides or UV light. The mechanism is illustrated for aldehydes but is similar for the other compounds ... 

In the preceding eqnation, the primary anion-radical gives the l-chloro-2,2,2-trifluoroethyl radical. In vivo, this radical was detected by the spin-trapping method (Poyer et al. 1981). Ahr et al. (1982) had presented additional evidence for the formation of the radical as an intermediate in halo-thane metabolism and identified l-chloro-2,2-difluoroethene as a product of radical stabilization. Metabolytic transformations of l-chloro-2,2-difluoroethene lead to acyl halides, which are relevant to halothane biotoxicity (Guengerich and Macdonald 1993). 

The insight that zinc ester enolates can be prepared prior to the addition of the electrophile has largely expanded the scope of the Reformatsky reaction.1-3 Substrates such as azomethines that quaternize in the presence of a-halo-esters do react without incident under these two-step conditions.23 The same holds true for acyl halides which readily decompose on exposure to zinc dust, but react properly with preformed zinc ester enolates in the presence of catalytic amounts of Pd(0) complexes.24 Alkylations of Reformatsky reagents are usually difficult to achieve and proceed only with the most reactive agents such as methyl iodide or benzyl halides.25 However, zinc ester enolates can be cross-coupled with aryl- and alkenyl halides or -triflates, respectively, in the presence of transition metal catalysts in a Negishi-type reaction.26 Table 14.2 compiles a few selected examples of Reformatsky reactions with electrophiles other than aldehydes or ketones.27... 

Eisenberg and co-workers (135-137) investigated dithiolene-containing organometallic complexes of Rh and Ir. Addition of an alkyl halide to [Rh(CO)-(PPh3)(mnt) forms a Rh(III) halo acyl complex. The halide can be stripped off by Ag+ salts (135) (Eqs. 30 and 31). 

Addition of acyl halides to olefins in the presence of catalytic amounts of aluminum chloride, stannic chloride, or zinc chloride gives /3-halo ketones. An example is the addition of propionyl chloride to ethylene... 

NaBOs and NaBr adds two bromine atoms across a triple bond. With allenes it is easy to stop the reaction after only 1 equivalent has added, to give X C CX=C. Addition of halogen to ketenes gives a-halo acyl halides, but the yields are not good. 

An acyl and an acyloxy group can be added to a double bond by treatment with an acyl fluoroborate and acetic anhydride. As expected, the addition follows Markovnikov s rule, with the electrophile Ac going to the carbon with more hydrogens. In an analogous reaction, an acyl and an amido group can be added to give 183, if a nitrile is used in place of the anhydride. Similarly, halo acetoxyla-tion is known.This reaction has also been carried out on triple bonds, to give the... 

The halo quinones (363) undergo photochemical acylation to afford the acyl (364) and the quinol derivatives (365). - The sunlight irradiation of acetic anhydride solutions of the quinone (366) affords the triquinone product (367). Irradiation of (366) in acetone also affords (367) but in addition the diquinone (368) is formed by a free radical path initiated by the abstraction of hydrogen from the amino group by excited state acetone. 

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