Reduction, acid chlorides organic

Metallic sodium. This metal is employed for the drying of ethers and of saturated and aromatic hydrocarbons. The bulk of the water should first be removed from the liquid or solution by a preliminary drying with anhydrous calcium chloride or magnesium sulphate. Sodium is most effective in the form of fine wire, which is forced directly into the liquid by means of a sodium press (see under Ether, Section II,47,i) a large surface is thus presented to the liquid. It cannot be used for any compound with which it reacts or which is affected by alkalis or is easily subject to reduction (due to the hydrogen evolved during the dehydration), viz., alcohols, acids, esters, organic halides, ketones, aldehydes, and some amines. 

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 scope of catalytic hydrogenations continues to be extended to more difficult reductions. For example, a notoriously difficult reduction in organic synthesis is the direct conversion of carboxylic acids to the corresponding aldehydes. It is usually performed indirectly via conversion to the corresponding acid chloride and Rosenmund reduction of the latter over Pd/BaS04 [65]. Rhone-Poulenc [30] and Mitsubishi [66] have developed methods for the direct hydrogenation of aromatic, aliphatic and unsaturated carboxylic acids to the corresponding aldehydes, over a Ru/Sn alloy and zirconia or chromia catalysts, respectively, in the vapor phase (Fig. 1.18). 

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). ... 

The air-sensitive Cp-substituted hydridovanadium complex is obtained by hydrogenolysis of the corresponding methyl derivative. The corresponding anionic compound is obtained by reduction of CpV(CO)4 with sodium and protonation with water (Scheme 64). Thus obtained [CpVH(CO)3] (106) is a useful one-electron reductant to reduce bromo- and iodoalkanes, bromoalkenes, and arylbromides in THF. Furthermore, acid chlorides are reduced to the aldehydes. A similar reduction with (106) is performed by using phase-transfer conditions in the presence of tetrabutylammonium hydrogen sulfate. Nitro compounds and organic halides are reduced under these conditions. 

Alkyl and acyl derivatives (28, 30) of 14-aminocodeinones (13, 26) and dihydro-codeinones (20a, 27) are readily prepared acylation is achieved under standard conditions of acid chloride or acid anhydride in the presence of an organic base, while alkylation can be achieved directly with an alkyl halide or by acylation and then lithium aluminium hydride reduction (Scheme 5). In this latter method the 6-keto group is protected as an acetal [8, 9, 18, 19]. For direct alkylation with unactivated alkyl halides, carrying out the reaction in a sealed tube at 120 °C has... 

The preparation of each is easy and this is the route to 87/88 as described by Evans11 in Organic Syntheses. Reduction of the free acid 91 with the borane-dimethylsulfide complex is easy if smelly and the rest is straightforward. The same auxiliary 87 can be used with any acid acylation with the acid chloride gives the chiral derivative 93 ready for enolate formation. 

Access to the aldehyde function has always been very important in organic chemistry. The two main transformations to introduce this function are oxidation of a primary alcohol to the aldehyde or reduction of an acid derivatives to the aldehyde. This second reaction has not found any general simple solution. If some progress has been made, the main methods used today are either the Rosenmund10 reaction on the acid chloride, reduction of the ester using a sophisticated hydride, or reduction of the ester to the alcohol followed by reoxidation of the alcohol function to the aldehyde. 

Storage Moisture-sensitive refrigerate store beiow 4 C handie and store under nitrogen Uses Reducing agent in electronic/chemical industry, prod, of printed circuit boards, electrodeless coatings selective reduction in organic synthesis, esp. aldehydes, ketones, and acid chlorides... 

Di-t-butylmethylsilane reducing agent, selective activity organic reduction reactions Triisobutylaluminum reducing agent, selective acid chloride synthesis... 

The cationic cyclization of polyisoprene with acid catalysts is well documented. The same reaction in polybutadienes requires much more severe conditions, higher temperatures and more acidic catalysts, and until recently has received much less attention. A cyclized polymer with a reduction of 35—40% of the initial unsaturation, can be prepared by treating cis-l,4-polybutadiene with an alkyl aluminium chloride-organic halide catalyst in xylene solution at >100 C."- Such polymers, containing polycyclic sequences apparently at random within the chains, have better skid resistance and tensile properties than the parent polymer. Cyclization has been reported to accompany other reactions in polydienes, for example the radiation-induced addition of carbon tetrachloride to 1,2-polybutadiene, and the direct addition of a o j unsaturated carboxylic acids (acrylic and cinnamic) to polydienes and polypentenamers. It is reported that the thermal isomerization of cis-transoidal poly(phenylacetylene) is accompanied by cyclization, and additionally chain scission and aromatization at temperatures >120°C. ... 

An attractive pathway with a lot of potential uses the transition metal mediated reaction of organic halides with carbon monoxide. Suitable substrates are organic halides capable of oxidative addition to low-valent transition metal compounds. Insertion of carbon monoxide and reductive elimination of an acid halide will complete the catalytic cycle. In tins way it was shown tiiat allyl chloride yields butenoic acid chloride in >80% yield accor g to equation 22)P As well as palladium, rhodium and iridium also act catalytically. It is of no surprise that allylic halides, benzylic halides and aryl halides in particular are readily converted to acid halides. Simple aliphatic halid undergo the oxidative addition step more slowly and, if they cany hydrogen atoms on an sf hybridized C atom in the -position to the halogen atom, may give alkenes via 3-hydrogen elimination. Alkenes can also be converted to acid halides widi carbon monoxide in the presence of transition metal catalysts in solvents such as methylene chloride or tetrachloromethane. ... 

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