Reduction of acid chlorides to aldehydes

Reduction of Acid Chlorides to Aldehydes. Palladium catalysis of acid chlorides to produce aldehydes is known as the Rosenmund reduction and is an indirect method used in the synthesis of aldehydes from organic acids. 

The organosilane reduction of acid chlorides to aldehydes has been accomplished in high yields with the use of the pentacoordinated organosilane 60 (Eq. 137).107 This transformation has been reported to occur with tribenzylsilane and triethylsilane, but yields were not reported.285,286... 

Hydrogenation reduction of acid chloride to aldehyde using BaS04-poisoned palladium catalyst. Without poison, the resulting aldehyde may be further reduced to alcohol. 

Reduction of acid chlorides to aldehydes. Two laboratories12 have published details for this reduction. One difficulty is the large quantities of reagent needed for preparative-scale reactions. For large-scale reductions the Rosenmund reaction is preferable. 

Reduction of aromatic azides. Aromatic azides can be reduced to anilines by this reagent in CHCl3 at 25°. The rate is accelerated by electron-withdrawing substituents but is reduced by electron-attracting groups. Even so, the presence of an azide group does not interfere with use of the reagent for reduction-of acid chlorides to aldehydes. 

E. Mosettig, R. Mozingo, The Rosenmund Reduction of Acid Chlorides to Aldehydes, Org. React. 1948, 4, 362-377. 

Table 23 Reduction of acid chlorides to aldehydes. Reproduced with permission from Elsevier...

The aldehyde intermediate can be isolated if a leas puwerfu] reducintt agent such as lithiu.ni trt>lerl but0xyalurniiiii3n hydride is ii. ed in place of LiAlH. This reagent, which is obtained by reaction of LiAlK with 3 cciuiv-alente of lerl-butyl alcohol, is particularly effective far carrying out the partial reduction of acid chlorides to aldehyde (Section 19.2>. 

Reduction of acid chlorides to aldehydes One of the most useful synthetic transformations in organic synthesis is the conversion of an acid chloride to the corresponding aldehyde without over-reduction to the alcohol. Until recently, this type of selective reduction was difficult to accomplish and was most frequently effected by catalytic hydrogenation (the Rosenmund reduction section 6.4.1). However, in the past few years, several novel reducing agents have been developed to accomplish the desired transformation. Among the reagents that are available for the partial reduction of acyl chlorides to aldehydes are bis(triphenylphosphine)cuprous borohydride , sodium or lithium tri-terf-butoxyaluminium hydride, complex copper cyanotrihydridoborate salts °, anionic iron carbonyl complexes and tri-n-butyltin hydride in the presence of tetrakis(triphenylphosphine)palladium(0). ... 

Roxenmundreduction H, ) 5). Peters and VanBekkum have described a convenient modification of (he Rosenmund reduction of acid chlorides to aldehydes. The method is based on a procedure of Japanese chemists- which has received little attention. Palladium-on-charcoal is used as the cataly.st, eihyidiisopropylamine as the hydrogen chloride acceptor, and acetone as the solvent (the hydrochloride of the amine is soluble in acetone). The reduction takes place at room temperature and atmospheric pressure. 

The use of both types of modifier to influence the selectivity of heterogeneous catalysts is not new. It has long been known, for example, that modifiers can have a powerful selectivity-enhancing effect in catalytic hydrogenation the Rosenmund reduction of acid chlorides to aldehydes is an early example of this. Another well-known modifier effect is rate and selectivity enhancement by bismuth in precious metal-catalyzed oxidations (Section 9.3). We feel, however, that the enormous po-... 

The reduction of acid chlorides to aldehydes under mild conditions has been achieved using [HFe(CO)4] [equation (1)]. The reaction generally proceeds in... 

Alexander Mikhaylovich Saytzev (Saytzeff) (Kazan 20 June 1841 (O.S.)-2 September 1910) studied with Kolbe in Marburg and Leipzig, and was professor in the University of Kazan. He discovered the synthesis of primary and secondary alcohols from esters, ketones, and aldehydes by the action of zinc and alkyl iodides (see Reformatsky, p. 858). He also discovered aliphatic sulphoxides. His brother Mikhayl Mikhaylovich (b. Kazan, 30 August 1845), at first his assistant and later manager of a chemical works in Kazan, discovered the reduction of acid chlorides to aldehydes by hydrogen gas in presence of palladium. ... 

G. W. J. Fleet, C. J. Fuller, and P. J. C. Harding. Bis(triphenylphosphine) copper(i) tetra-hydroborate in the reduction of acid chlorides to aldehydes. Tetrahedron Letters, 1978, 16, 1437. 

R. A. W. Johnstone and R. P. Telford. Metal-assisted borohydride reduction of acid chlorides to aldehydes. J.G.S. Ghent. Gomm., 1978, 354. 

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. ... 

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