Metal hydrides acyl halides

Acyl halides are reduced to alcohols by L1A1H4 or NaBH4, as well as by other metal hydrides (Table 19.5), but not by borane. 

ACID ANHYDRIDES, ACYL HALIDES, ALKALI METALS ALKYLALUMINIUM DERIVATIVES, ALKYLNON-METAL HALIDES COMPLEX HYDRIDES, METAL HALIDES, METAL HYDRIDES METAL OXIDES, NON-METAL HALIDES (AND THEIR OXIDES)... 

In their zerovalent compounds, all three metals (Ni, Pd, Pt) undergo oxidative addition of alkyl, aryl, and acyl halides. For palladium, in particular, such reactions are key steps in a wide range of catalytic reactions. Palladium(II) and platinum(II) complexes also add C—X bonds to generate Pd(IV) and Pt(IV) species. Since C—C or C—H bond formation by reductive elimination often occurs readily, a common reaction sequence involves C—X addition followed by coupling of two alkyl groups, or an alkyl and a hydride ligand. 

The product of the initial reduction is most often more reactive than the starting material therefore a second addition is very common (AdN then Ep, then AdN, covered in Section 9.2). An Ad f then Ep product can be obtained with acyl halides and one equivalent of a less reactive metal hydride at low temperature. Borohydrides selectively react with aldehydes and ketones in the presence of less reactive esters and amides. 

Sodium/ammonia" treatment also causes disruption of the ring in thiophene and simple thiophenes, however thiophene-2-carboxylic acid and 2-acyl-thiophenes can be converted into the 2,5-dihydro derivatives using lithium in ammonia, followed by protonation or trapping with an alkyl halide."" Side-chain reductions can be carried out with metal hydrides, which do not affect the ring. 

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