Carboxylic acids parent hydrides

Conversion of Acid Chlorides into Alcohols Reduction Acid chlorides are reduced by LiAJH4 to yield primary alcohols. The reaction is of little practical value, however, because the parent carboxylic acids are generally more readily available and can themselves be reduced by L1AIH4 to yield alcohols. Reduction occurs via a typical nucleophilic acyl substitution mechanism in which a hydride ion (H -) adds to the carbonyl group, yielding a tetrahedral intermediate that expels Cl-. The net effect is a substitution of -Cl by -H to yield an aldehyde, which is then immediately reduced by UAIH4 in a second step to yield the primary alcohol. 

Retained names of carboxylic acids may also be modified to name amides, nitriles and aldehydes, by changing the -ic acid ending to -amide, -onitrile or -aldehyde. Names such as formaldehyde, acetonitrile and propionamide result. Of these, only acetonitrile may be treated as a functional parent hydride. 

Substituent groups (or substituents), considered as replacing hydrogen atoms in parent hydrides, are named using appropriate suffixes ( ol , thiol , peroxol , carboxylic acid , etc.) and prefixes ( hydroxy , phosphanyl , bromo , nitro , etc.). Substituent suffixes are ranked in Section P-43 of Ref. 1. Prefixes are extensively listed in Appendix 2 of Ref. 1. The case of substituents formed by removal of one or more hydrogen atoms from a parent hydride is explained briefly, with examples, in Section IR-6.4.7, and prefixes for many common inorganic substituents are included in Table IX. 

Acylimidazoles and Nucleophiles. Acylimidazoles are readily prepared from the parent carboxylic acids by reaction of the derived acid chloride with imidazole or directly using N,N -Carbonyldiimidazole. These intermediates react smoothly with a variety of nucleophiles including Grignard reagents (eq 3), Lithium Aluminum Hydride (eq 4), and nitronates (eq 5). At —20 ""C, aroylimidazoles can be reduced to the corresponding aldehydes in the presence of an ester function. ... 

The parent system (99) has been obtained by lithium aluminum hydride reduction of perhydro-imidazo[l,5-a]pyridine-l,3-dione (from ethyl 2-piperidine carboxylate and cyanic acid) and by ring closure of 2-aminomethylpiperidine with formaldehyde. 3-Substituted derivatives have also been described. The 3-phenyl- and 3-/-butyl derivatives (but not the propyl and benzyl derivatives) show ring-chain tautomerism (70JHC355). 

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