Hydration of dienes

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating Hgands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19]. In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

Several cationic palladium(II) aqua complexes, [Pd(H20)4], cis-[PdL(H20)2] (L = en, methionine methyl ester, l,5-dithiacycloocta-3-ol), and [Pd(dien)(H20)], serve as the active catalyst for the selective hydration of various nitriles to the corresponding carboxamides, e.g., CHCI2CN was hydrated to CHCl2C(0)NH2 in the presence of... 

The addition of carboxylic acids to bicyclo[2.2.1]hepta-2,5-diene has been described by several authors the method described here is a modification of these procedures. Nortricyclanol has been prepared by the hydration of bicyclo[2.2.1]hepta-2,5-diene and the solvolysis of nortricyclyl and bicyclo[2.2.1]hept-2-en-5-yl halides, as well as by the saponification and... 

For a decade or so [CoH(CN)5] was another acclaimed catalyst for the selective hydrogenation of dienes to monoenes [2] and due to the exclusive solubility of this cobalt complex in water the studies were made either in biphasic systems or in homogeneous aqueous solutions using water soluble substrates, such as salts of sorbic add (2,4-hexadienoic acid). In the late nineteen-sixties olefin-metal and alkyl-metal complexes were observed in hydrogenation and hydration reactions of olefins and acetylenes with simple Rii(III)- and Ru(II)-chloride salts in aqueous hydrochloric acid [3,4]. No significance, however, was attributed to the water-solubility of these catalysts, and a new impetus had to come to trigger research specifically into water soluble organometallic catalysts. 

Hydrocyanation of olefins and dienes is an extremely important reaction [32] (about 75 % of the world s adiponitrile production is based on the hydrocyanation of 1,3-butediene). Not surprisingly, already one of the first Rhone Poluenc patents on the use of water soluble complexes of TPPTS described the Ni-catalyzed hydration of butadiene and 3-pentenenitrile (Scheme 9.10). The aqueous phase with the catalyst could be recycled, however the reaction was found not sufficiently selective. 

Hunsdiecker reaction, 9, 5 19, 4 Hydration of alkenes, dienes, and alkynes, 13, 1... 

The products obtained via the acid-catalyzed hydration of conjugated dienes are dependent on the structure of the diene. Thus, through the use of deuterated reagents, the sulfuric acid-catalyzed hydration of 1,3-cyclohexadiene was shown to proceed exclusively by a 1,2 addition (equation 194).293... 

On the other hand, the hydration of acyclic dienes such as 1 - or 2-substituted 1,3-butadienes affords an equilibrium mixture of allylic alcohols resulting from both 1,2- and 1,4-addition (equation 195).296... 

Catalytic conversions were experimentally studied in Russia toward the end of the nineteenth century, and especially in the twentieth century, and regularities were empirically established in a number of cases. The work of A. M. Butlerov (1878) on polymerization of olefins with sulfuric acid and boron trifluoride, hydration of acetylene to acetaldehyde over mercury salts by M. G. Kucherov (1881) and a number of catalytic reactions described by V. N. Ipatieff beginning with the turn of the century (139b) are widely known examples. S. V. Lebedev studied hydrogenation of olefins and polymerization of diolefins during the period 1908-13. Soon after World War I he developed a process for the conversion of ethanol to butadiene which is commercially used in Russia. This process has been cited as the first example of commercial application of a double catalyst. Lebedev also developed a method for the polymerization of butadiene to synthetic rubber over sodium as a catalyst. Other Russian chemists (I. A. Kondakov I. Ostromyslenskif) were previously or simultaneously active in rubber synthesis. Lebedev s students are now continuing research on catalytic formation of dienes. 

Nafion-H is a convenient acid catalyst for pinacolone rearrangements. Hydration of acetylenes can be conducted with Nafion-H impregnated with mercury(II) ions. Diels-Alder catalyst. This protic resin catalyzes Diels-Alder reactions, but longer reaction times are needed than in reactions catalyzed by Lewis acids. The reactions are generally conducted in refluxing benzene or chloroform. In the case of dienes that polymerize readily, the reaction is conducted at room temperature for 1-2 days.°... 

The results above suggested that selective monooxymercuration of dienes is possible, and indeed this has been realized. In the ease of symmetrical dienes such as 1,5-pentadiene, the yield of enol is lower than predicted for a statistical reaction (50 % enol) the statistical value is approached in longer chain dienes. Yields can be raised by using mercuric trifluoroacctate(2,195). In the case ofunsymmelricaldienesselective hydration can be achieved. Thus limonene (1) can be converted to the enol (2) in 70% yield. 

Addition of water to dienes is catalyzed by palladium complexes. The reaction has been used for synthesizing unsaturated alcohols and ethers from aliphatic conjugated C4 and Cg olefins 248). In particular, the hydration of butadiene with water in the presence of bis(2,4-pentane-dionato)palladium and triphenylphosphine gave 2,7-octadien-l-ol, l,7-octadien-3-ol, and 1,3,5,7-octatetraene 18). The reaction was accelerated by carbon dioxide. Compounds Pd(PPh3)4 and Pd(02C0)-(PPh3)2 were also effective. 

O. R. XIII-3, C. Walling, and E. S. Huyser, Free Radical Additions to Olefins and Acetylenes to Form Carbon-Carbon Bonds XI11-1, G. Zweifel and H. C. Brown, Hydration of Olefins, Dienes, and Acetylenes via Hydroboration XIII-2, W. E. Parham and E. E. Schweizer, Halocyclopropanes from Halocarbenes. ... 

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