Sodium borohydride-Cadmium chloride

Sodium amalgam, 183, 326 Sodium-Ammonia, 355-356 Sodium benzeneselenoate, 356 Sodium bis(2-methoxyethoxy)aluminum hydride, 357,448 Sodium borohydride, 357-359 Sodium borohydride-Cadmium chloride, 359... 

Sodium borohydride-Cadmium chloride 1.5 DMF. The salt is obtained by crystallization of CdCl2-2.5 H20 from DMF. 

Reduction of RCOCI to RCHO. Sodium borohydride and this cadmium salt reduce acyl chlorides to aldehydes, but only in solvents such as DMF, DMA, and HMPT. DMF is essential, but the amount of DMF in the salt is sufficient. For the most part, yields are 50-90%. Aryl, alkyl, and benzylic halides do not react. Other functional groups (nitrile, nitro, ester, C=C) are also inert. 

RCOClECHO. Acid chlorides are reduced at 0° to aldehydes in 60-757 yield by sodium borohydride in the presence of cadmium chloride and DMF. Yields are low in the absence of either the salt or DMF. Some of the corresponding alcohol is usually formed ... 

Reductive Methods.—Aldehydes from Acid Derivatives. Acid chlorides are reduced to aldehydes by sodium borohydride in the presence of cadmium(il)... 

Other Preparations.—Carboxylic acids have been converted into aldehydes through di-isobutylaluminium hydride reduction of 3-acylthiazolidine or 2-thiazoline-2-thiol ester intermediates. Bis(triphenylphosphine)copper(l) tetrahydroborate, (Ph3P)2CuBH4, shows promise as a new reagent for the reduction of acid chlorides to aldehydes. The same conversion can be accomplished using sodium borohydride in a mixture of acetonitrile and hexamethyl-phosphoramide containing a cadmium(il) chloride-dimethylformamide complex. ... 

Zinc-modified cyanoborohydride, prepared from anhydrous zinc chloride and sodium cyanoborohy-dride in the ratio 1 2 in ether, selectively reduced aldehydes and ketones but not acids, anhydrides, esters and tertiary amides. In methanol the reactivity paralleled the unmodified reagent. Zinc and cadmium borohydrides form solid complexes with DMF, which may prove to be convenient sources of the reducing agents.Aromatic and a,p-unsaturated ketones were reduced much more slowly than saturated ketones, so chemoselective reduction should be possible. 

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