Differente comportamento di alogenuri acilici verso formali agenti omologanti trialometilici

Acyl halides are carboxylic acid derivatives commonly used as electrophiles in organic chemistry in which the -OH group of the acid is replaced by a halogen atom. Common acyl halides are acyl fluorides and chlorides. Acyl fluorides display a very good balance between stability and reactivity, instead chlorides are less stable and more reactive derivatives. The aim of this work was to investigate the different behavior of acyl chlorides and fluorides towards formal trihalomethyl-homologating agents. The trihalomethyl carbanion used for the reaction is easily generated after treatment of a carbon tetrahalide with hexamethylphosphorous triamide and is let to react with the chosen acyl halide under Barbier conditions at low temperatures. The reaction showed an interesting divergent behavior giving two different products (maintaining the same conditions) just by changing the starting acyl halide. In the work a total of 22 examples for the two reactions are reported both with carbon tetrachloride and carbon tetrabromide. Electronic nature of substituents did not affect the course of the reaction, while the substitution pattern seemed to affect the procedure involving acyl fluorides. The two reactions that have been studied represent two new synthetic procedures to access 2-halo-1,3-diones and β-dihaloeneol esters with unprecedented simplicity in just one straightforward reaction step. Moreover, the products obtained from the reactions are valuable substrates presenting both electrophilic and nucleophilic sites in the same molecule thus they can be further transformed and functionalized with ease to obtain even more complex products.