Diacetoxy-1,3-butadiene

Then, pseudo-p-DL-gulopyranose (14) was synthesized by hydroxylation of 2,5-di-hydroxy-3-cyclohexene-l-methanol triacetate (12), which was prepared by Diels-Alder cycloaddition of 1,4-diacetoxy- 1,3-butadiene (10) and allyl acetate (11), with osmium tetroxide and hydrogen peroxide and successive acetylation as the pentaacetate (13). Analogous hydrolysis of 13 in ethanolic hydrochloric acid afforded the free pseudosugar 14 in 33% yield from 12 [2] (Scheme 7). 

B. trans, trans-, A-Diacetoxy-, 3-butadiene. The diacetate above (83.0 g., 0.373 mole), dimethyl acetylenedicarboxylate2 (54.0 g., 0.380 mole), and benzene (250 ml.) are placed in a 500-ml. flask and boiled under reflux for 6 hours (Note 7). The solution is filtered to remove the remaining mercury and mercuric salts, and the benzene is distilled under reduced pressure. The residual viscous yellow oil is distilled under reduced pressure (Note 8). A mixture of l,4-diacetoxy-l,3-butadiene and dimethyl phthalate is collected at 140-155° (18-20 mm.), bath temperature 170-200°, from which the diene crystallizes as colorless needles in the cooled receiver. The solid in the receiver is broken up and washed onto a Buchner funnel with petroleum ether (b.p. 60-70°). The solid is then pressed between sheets of filter paper to remove excess dimethyl phthalate and recrystallized from acetone-petroleum ether (b.p. 60-70°) (ca. 1 2) (Note 9). The yield of colorless needles of trans,trans- 1,4-diacetoxy-1,3-butadiene, m.p. 102-104°, is 26-31 g. (41-49%) (Notes 10, 11, and 12). 

Diacetoxy-1,3-butadiene is a reactive diene in the Diels-Alder reaction. It has been used as the starting material in stereospecific syntheses of conduritol-D8 and shikimic acid,9,10 and in a simple general method of preparation of benzene derivatives, especially unsymmetrical biphenyls.11,12... 

Biphenyls are also by-products of acetoxylation of aromatics [92]. Their formation is favored with a palladium metal catalyst in the absence of oxidants [93-95]. Vinyl acetate undergoes oxidative coupling under similar conditions to form 1,4-diacetoxy-1,3-butadiene [99], and aromatics and heterocycles can substitute an olefinic H-atom [100] according to eq. (28) (with X = H, CN, AcO, EtO) [100-102]. 

The Diels-Alder condensation of l ,4 -diacetoxy-1,3-butadiene with butyl glyoxylate leads to a 1 1 mixture of butyl l,4-di-0-acetyl-2,3-dideoxy-a-DL-threo- and -e/y/Aro-hex-2-enuronates (282 and 283) in 75% total yield. These compounds appear to be excellent substrates for further conversion to the full sugars by the direct addition of appropriate reagents to the double bond. 

An oxidative coupling of vinyl acetate with the catalyst palladiiun acetate was reported by Kohll and van Helden of Shell research [61]. They observed the formation of 1,4-diacetoxy-1,3-butadiene which was hitherto available only from cumbersome multistep syntheses (Equation 44). 

The Structures and Reactions of Hydroxy-, Mercapto-, and Aminothiophens. - 3-Thiolen-2-one reacts as dienophile with 2,3-dimethyl-1,3-butadiene, 1,3-cyclohexadiene, 1,1-(ethylenedioxy)-2,3,4,5-tetrachlorocyclopentadiene and (E),(e)-l,4-diacetoxy-1,3-butadiene to give (114), (115), (116), and (117), respectively. 

Difunctionalization with similar or different nucleophiles has wide synthetic applications. The oxidative diacetoxylation of butadiene with Pd(OAc)i affords 1,4-diacetoxy-2-butene (344) and l,2-diacetoxy-3-butene (345). The latter can be isomerized to the former. An industrial process has been developed based on this reaction. The commercial process for l,4-diacetoxy-2-butene (344) has been developed using the supported Pd catalyst containing Te in AcOH. 1,4-Butanedioi and THF are produced commercially from 1,4-diacetoxy-2-butene (344)[302]. 

The first step is the liquid phase addition of acetic acid to butadiene. The acetoxylation reaction occurs at approximately 80°C and 27 atmospheres over a Pd-Te catalyst system. The reaction favors the 1,4-addition product (l,4-diacetoxy-2-butene). Hydrogenation of diacetoxybutene at 80°C and 60 atmospheres over a Ni/Zn catalyst yields 1,4-diacetoxybu-tane. The latter compound is hydrolyzed to 1,4-butanediol and acetic acid ... 

The most important reaction is the oxidative addition of two moles of acetic acid to butadiene to form 1,4-diacetoxy-2-butene (21) with the reduction of Pd2+ to Pd°. In this reaction, 3,4-diacetoxy-l-butene (127) is also formed. In order to carry out the reaction catalytic with regard to Pd2+, a redox system is used. This reaction attracts attention from the standpoint of industrial production of 1,4-butanediol. For this purpose, the formation of 127 should be minimized. Numerous patent applications have been made (examples 113-115), but no paper treating the systematic studies on the reaction has been published. 

Diacetoxylation of 1,3-butadiene is a process that drew much attention since the product l,4-diacetoxy-2-butene may be converted to 1,4-butanediol and tetrahydro-furan by further transformations (see Section 9.5.2). The liquid-phase acetoxylation of 1,3-butadiene in a Wacker-type system yields isomeric 1,2- and cis- and trans-1,4-diacetoxybutenes ... 

Diacetoxy-2-butene. Mitsubishi commercialized a new proces, the acetoxy-lation of 1,3-butadiene, as an alternative to the Reppe (acetylene-formaldehyde) process for the production of l,4-diacetoxy-2-butene. l,4-Diacetoxy-2-butene is tranformed to 1,4-butanediol used in polymer manufacture (polyesters, polyurethanes). Additionally, 1,4-butanediol is converted to tetrahydrofuran, which is an important solvent and also used in polymer synthesis. 

A somewhat similar hydrogenation problem arose in a different approach to 1,4-butanediol and tetrahydrofuran.345 In the process developed by Mitsubishi, 1,3-butadiene first undergoes Pd-catalyzed diacetoxylation to yield 1,4-diacetoxy-2-butene. To avoid the further transformation of the diol as in the abovementioned process, l,4-diacetoxy-2-butene is directly hydrogenated in the liquid phase (60°C, 50 atm) on traditional hydrogenation catalysts to produce 1,4-diacetoxybutane in 98% yield, which is then hydrolyzed to 1,4-butanediol. 

The selectivity in the formation of 1,4-diacetoxy-2-butene (1,4-DAB) is considerably enhanced when tellurium compounds are used as cocatalysts. Thus a heterogeneous catalyst, prepared by impregnation of Pd(N03)2 and Te02 dissolved in HN03 over active charcoal (Pd/Te = 10), can be used for the oxidation of butadiene (by 02 in AcOH at 90 °C) to 63% trans-l,4-DAB, 25% cis-1,4-DAB and 12% 3,4-diacetoxy-l-butene. Conventional soluble catalysts such as Pd(OAc)2/Li(OAc) are much less selective in the formation of 1,4-DAB 429 The gas-phase 1,4-diacetoxylation of butadiene in the presence of Pd-Te catalysts is currently being industrially developed by Mitsubishi and BASF 430... 

The in situ regeneration of Pd(II) from Pd(0) should not be counted as being an easy process, and the appropriate solvents, reaction conditions, and oxidants should be selected to carry out smooth catalytic reactions. In many cases, an efficient catalytic cycle is not easy to achieve, and stoichiometric reactions are tolerable only for the synthesis of rather expensive organic compounds in limited quantities. This is a serious limitation of synthetic applications of oxidation reactions involving Pd(II). However it should be pointed out that some Pd(II)-promoted reactions have been developed as commercial processes, in which supported Pd catalysts are used. For example, vinyl acetate, allyl acetate and 1,4-diacetoxy-2-butene are commercially produced by oxidative acetoxylation of ethylene, propylene and butadiene in gas or liquid phases using Pd supported on silica. It is likely that Pd(OAc)2 is generated on the surface of the catalyst by the oxidation of Pd with AcOH and 02, and reacts with alkenes. 

Dihydro-phosphol-l-oxide konnen andererseits als Dienophile in der [4+2]-Cyclo-addition fungieren. So erhalt man aus l-Phenyl-4,5-dihydro-phosphol-l-oxid und 1,4-Diacetoxy-l,3-butadien beim Erhitzen auf 150° l-Phenyl-2,3-dihydro-l-benzophos-phol-l-oxid (Schmp. 97-101°) in 50%iger Ausbeute434 ... 

The C5 aldehyde intermediate is produced from butadiene via catalytic oxidative acetoxylation followed by rhodium-catalyzed hydroformylation (see Fig. 2.30). Two variations on this theme have been described. In the Hoffmann-La-Roche process a mixture of butadiene, acetic acid and air is passed over a palladium/tellurium catalyst. The product is a mixture of cis- and frans-l,4-diacetoxy-2-butene. The latter is then subjected to hydroformylation with a conventional catalyst, RhH(CO)(Ph3P)3, that has been pretreated with sodium borohydride. When the aldehyde product is heated with a catalytic amount of p-toluenesulphonic acid, acetic acid is eliminated to form an unsaturated aldehyde. Treatment with a palladium-on-charcoal catalyst causes the double bond to isomerize, forming the desired Cs-aldehyde intermediate. 

Similarly, reaction of 1,4-diacetoxy-l,3-butadiene with methyl glyoxalate afforded glu-curonate glycal [228] and a 2,3-unsaturated isomer. Cycloaddition reactions performed on substrates with inverse electronic properties (e. g., enol ether as a dienofile and unsaturated carbonyl compound as a heterodiene) afford not only the expected products but also ones having high endo selectivity [229,230] as exemplified below by olivose 126 synthesis (O Scheme 43). 

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