Metal carbonyls chloride catalysis

The first experiments which were carried out in the author s laboratory on organometallic phase-transfer catalysis were concerned with the reduction of nitrobenzenes (4) to anilines (5) by triiron dodecacarbonyl. Such a conversion was reported to occur in benzene containing methanol at reflux for 10-17 h, with the hydridoundecacarbonyltriferrate anion as the likely key intermediate (16). It was our expectation that the trinuclear iron hydride should be generated by phase-transfer catalysis and if so, effect reduction of nitro compounds (4) under exceedingly mild conditions. Indeed this was the case, as illustrated by the results shown in Table I (17). Not only is the reaction complete in 2 h or less using sodium hydroxide as the aqueous phase, benzene as the organic phase, and benzyltrieth-ylammonium chloride as the phase-transfer catalyst, but it occurs at room temperature and requires less metal carbonyl than when the reaction was... 

Carbonylation-Decarbonylation. These reactions constitute a large and important segment of the homogeneous catalytic literature. Catalysis by most of the group VIII noble metals has been found, and a variety of substrates have been converted. For example, olefins react with CO and PdCl2 or (< 3P)2PdCl2 to yield -chloroacyl chlorides (58) and unsaturated acyl chlorides (59), respectively, a, w-Dienes, such as... 

Recently, two methods were published that have attracted some interest, because no metal salts are necessary as oxidation reagents. Shi and Xu (1990) found that substituted (trifluoromethyl)-diazoalkanes (CF3CRN2, R = alkyl or aryl) are obtained by refluxing trifluoromethyl ketones and 2,4,6-tri(isopropyl)benzenesulfonyl hydrazone in a methanolic solution of KOH. Kumar (1991) synthesized a-diazocar-bonyl compounds under tri-phase phase-transfer catalysis using a polystyrene-supported (tributyl)(methyl)-ammonium chloride catalyst, methanesulfonyl chloride, NaN3, and methylsulfonyl azide in 1,2-dichloroethane and a carbonyl-activated substrate (69-94% yield). 

Carbonylation of allylic and benzylic chlorides was carried out by transition-metals (as catalysis) to give P,y-unsaturated acids. However, the above method gave low yields. It is found that carbonylation of benzyl bromide and chloride could be carried out by stirring with an aqueous sodium hydroxide and an organic solvent using a PTC and a cobalt catalyst. Even benzylic mercaptan could be carbonylated to give esters under high pressure and temperature (Scheme 142) ... 

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