Halogenated carbonyl

Hoffmann (1). a student of Hantzsch, used the condensation of selenobenzamide with a-halogenated carbonyl derivatives to prepare a series of 2-phenylselenazoles according to the Scheme 1,... 

The O-S exchange method in presence of a-halogenated carbonyl compound is a very good one for thiazole compounds. The thioamide is prepared in situ by the action of amide upon phosphorus pentasulphide with solvent. The a-halogenated aldehyde reacts directly. But the O-Se exchange cannot be performed with a-halogenated carbonyl compounds because of the apparition of phosphoric acid. (Scheme 3), The C-Se bond is very sensitive to add pH. 

The replacement of selenoamide by selenourea in the Hantzsch s synthesis. (1st method) leads to 2-aminoselenazoles 2, 14. 15). This series of compounds has been well developed, mainlv because selenourea is much more easily accessible than the selenoamides, but also because a wide variety of a-halogenated carbonyl compounds are available for the Hantzsch s evdization reaction (Scheme 5). 2-Aminoselenazole itself was prepared from commercially available chloroacetaldehyde semihydrate... 

With a-halogenated carbonyl derivatives such as a.a -dibromobiacetyl. Br-CH -C-C-CHi-Br. and selenourea, 2.2 -diamino-4,4 -biselenazole... 

Other important applications for organoboranes" include the Michael-like addition reaction to a ,/3-unsaturated carbonyl compounds, and the alkylation of a-halogenated carbonyl compounds. 

S-Alkylation of a thiocarboxylic acid with an a-halogenated carbonyl compound gives a thiol ester in which the two carbons to be connected... 

Thieno[2,3-. ]pyridines, 115, form via a condensation reaction with halogenated carbonyl compounds, as shown in Scheme 35. Depending on the base strength of the reagent and reaction conditions, intermediate 114 may be isolated <2005CCA63>. 

TABLE 13.8 Estimated Lifetimes of Halogenated Carbonyl Compounds in the Aqueous Phase11... 

The hydrogen and halogen carbonyls and the nitroso carbonyls Co(NO)(CO)3, in which all bonds are covalent, are non-polar compounds with relatively low boiling points. The dimeric carbonyl, too, is non-polar, but its boiling point is much higher than that of the monomeric carbonyls because of the larger size of the molecule. 

A large number of halogen carbonyls has been prepared some of them have not the 18-electron configuration in PtCl2(CO)2, for example, there are only sixteen electrons. The carbonyls always have eighteen electrons, but the number of ligands is variable. It is therefore doubtful that they have d2sp3 hybridization. 

The phosphonium salts derived from an o -hydroxybenzyl halide and triphenylphosphine react with a variety of a-halogenated carbonyl compounds in the presence of sodium methoxide to yield chromenes. The speed of the alkylation and the simplicity of the work-up make this an attractive route to 2- and 3-substituted chromenes. 

Die Perkov-Reaktion von Phosphinigsaure-estem mit Chloral565 ist zur Synthese weiterer neuer Phosphinsaure-ester angewandt578 580 sowie mit anderen 2-Halogen-carbonyl-Verbindungen durchgefiihrt worden z.B.581 ... 

Reactions with halogens. Carbonyl halide complexes are formed by the replacement of CO with a halogen to give products that usually obey the EAN rule. For example,... 

Aliphatic and aryl aliphatic amino ketones are made by the amination of the halogenated carbonyl compounds, - e.g., dimethylaminoacetone (74%), l-diethylamino-2-pentanone (79%), and a-methylaminopropio-phenone (57%). It is noteworthy that this system may undergo a rearrangement, viz., ArCOCH,Br+ (C,H,),NH— ArCHjCON(C,H5)a (45%). The reaction of a-halo ketones with arylamines is even more complex. Examples of the formation of a-aminoaldehydes by this method are few. However, the same results may be achieved by the amination of the halo acetals with subsequent hydrolysis. "... 

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