Halo acyl halide

Ketenes can be prepared by dehalogenation of a-halo acyl halides with zinc or with... 

Pyrolysis of carboxylic acids Dehydrohalogenation of acyl halides Dehalogenation of a-halo acyl halides Rearrangement of diazo ketones (Wolff)... 

Dehalogenation of a-Halo Acyl Halides Dihalo-elimination... 

Ketenes can be prepared by dehalogenation of ot-halo acyl halides with zinc or with tri-phenylphosphine.348 The reaction generally gives good results when the two R groups are aryl or alkyl, but not when either one is hydrogen.34,1 OS IV, 348 68, 41. 

A variety of halo acyl halides have been made by use of the above reagents. Table 61 includes examples of compounds containing halogen atoms in alpha, beta, gamma, and delta positions of an aliphatic carbon chain as well as on the aromatic nucleus. All four halogen elements are represented. 

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. 

GLYCOSIDES Tetraethylammonium bromide. Silver carbonate-Celite. o-HALO ACYL HALIDES N-Bromosuccinimide. 

The thiazolidin-4-one ring system has a wide variety of physiological activity, and its chemistry has been well investigated. By contrast, the 5-ones have been little studied. They are readily formed from thioureas and a-halo-acyl halides, e.g. (312). However, a slight modification of the substrate can lead to a variety... 

Cycloadditions of a-chloroketenes to fulvenes are well documented and the adducts have also been applied to the synthesis of other natural products, including ophiobolin, filifolone, and chrysanthemic acid (Scheme 7.4) [5]. Nevertheless, Hong and coworkers [6] reported a new mode of reaction between a-halo acyl halides and 6,6-dialkoxyfulvene 20. Under standard conditions of in situ generation of a-chloroketenes, nucleophilic acyl substitution of the acyl chloride by... 

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