Dimethyl carbonate reductive carbonylation

Me have studied the Co-I-PPh catalyzed reductive carbonylation of methanol, dimethyl ketalsf dimethyl carbonate and methyl esters ( 10 JL5 >2 ) 0 goal was to achieve high acetaldehyde... 

Reductive Carbonylation of Dimethoxy Ketals and Dimethyl Carbonate. Acetaldehyde is obtained via the reductive carbonylation of dimethyl ketals. Equation 12, and dimethyl carbonate. Equation 13 (15). 

In addition to the successful reductive carbonylation systems utilizing the rhodium or palladium catalysts described above, a nonnoble metal system has been developed (27). When methyl acetate or dimethyl ether was treated with carbon monoxide and hydrogen in the presence of an iodide compound, a trivalent phosphorous or nitrogen promoter, and a nickel-molybdenum or nickel-tungsten catalyst, EDA was formed. The catalytst is generated in the reaction mixture by addition of appropriate metallic complexes, such as 5 1 combination of bis(triphenylphosphine)-nickel dicarbonyl to molybdenum carbonyl. These same catalyst systems have proven effective as a rhodium replacement in methyl acetate carbonylations (28). Though the rates of EDA formation are slower than with the noble metals, the major advantage is the relative inexpense of catalytic materials. Chemistry virtually identical to noble-metal catalysis probably occurs since reaction profiles are very similar by products include acetic anhydride, acetaldehyde, and methane, with ethanol in trace quantities. 

Both permanganate and ozonolysis break the carbon-carbon double bond and replace it with carbonyl (C=0) groups. In the permanganate cleavage, any aldehyde products are further oxidized to carboxylic acids. In the ozonolysis-reduction procedure, the aldehyde products are generated in the dimethyl sulfide reduction step (and not in the presence of ozone), and they are not oxidized. 

More recently, Bouwman carried out a detailed study on the carbonylation of nitrobenzene in methanol with palladium bidentate phosphane complexes as catalysts [29-31]. After a careful analysis of the reaction, mixtures revealed that besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MFC), A, 7/-diphenylurea (DPU), aniline, azobenzene (Azo) and azoxyben-zene (Azoxy)], large quantities of oxidation products of methanol were co-produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H2O, and CO). They proposed the Pd-imido species P2Pd = NPh, which is the central key intermediate that can link together all the reduction products of nitrobenzene and all the oxidation products of methanol into one unified mechanistic scheme. 

As was reported by Romano et aL, cuprous chloride is an effective catalyst for selective dimethyl carbonate synthesis. The reaction proceeds at 90—100 C at >20 bar of CO and can be either separated into an oxidation and a reduction step, or carried out in a one-pot redox system [71]. Dimethyl carbonate is a versatile reagent which can replace phosgene and dimethyl sulfate as carbonylating and methylating agents, respectively. 

Carbonylation acetic acid, acetic anhydride, methyl acetate, methyl formate Reductive carbonylation acetaldehyde, ethanol, ethyl acetate, ethylidene diacetate Oxidative carbonylation dimethyl carbonate, dimethyl oxalate... 

Lower dialkyl sulfides are often employed as valuable solvents. Most organic sulfides with low molecular mass have intense unpleasant odors. Cotmnercial dimethyl sulfide contains highly malodorous impurities such as carbon disulfide, carbonyl sulfide, methyl thiol, dimethyidisulfide, hydrogen sulfide and other sidfurous compounds at low levels. Dialkyl sulfide borane complexes of high purity are used to produce low odor dialkyl sulfides by enantioselective reduction. ... 

Borane (as BH3 in tetrahydrofuran or dimethyl sulfide) is an even milder reducing agent than BH4G for the carbonyl group of aldehydes and ketones. This difference in reactivity can be used to advantage when selective reduction is necessary. For example, borohydride reduces a ketone carbonyl more rapidly than a carbon-carbon double bond, whereas borane reduces the carbon-carbon double bond more rapidly than carbonyl ... 

Before the modem era of organotransition metal reactivity, it was observed that nickel carbonyl reacted with 2-methallyl chloride in methanol to give methyl 3-methyl-3-butenoate and 2,5-dimethyl-1,5-hexadiene as a by-product. In THF at 25 °C, the diene was the exclusive product. This mild formation of a carbon carbon bond, and the interest in the synthesis of terpene-based natural products led to efforts to test the scope and limitations of the process. An obvious pathway involves stepwise oxidative addition of each aUyl unit followed by Reductive Elimination. As discussed below, the key intermediates (left vague in Scheme 48) are likely to involve Ni -Ni couples. 

The way they solved the problem was this. (S )-(-)-Malic acid is available cheaply. Its dimethyl ester 127 could be chemoselectively reduced by borane to give 128. Normally borane does not reduce esters and clearly the borane first reacts with the OH group and then delivers hydride to the nearer carbonyl group. The primary alcohol was chemoselectively tosylated 129 and the remaining (secondary) OH protected with a silyl group 130 (TBDMS stands for t-butyldimethylsilyl and is sometimes abbreviated to TBS). Now the remaining ester can be reduced to an aldehyde 131 and protected 132. Displacement of tosylate by cyanide puts in the extra carbon atom 133 and reduction gives 134, that is the dialdehyde 126 in which one of the two aldehydes is protected. This compound was used in the successful synthesis of lipstatin. 

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