Dehydrogenation 1,2-diols

The 1,4-isomer has been similarly generated from terephthalonitdle [623-26-7] (56) using a mixed Pd/Ru catalyst and ammonia plus solvent at 125 °C and 10 MPa (100 atm). It is also potentially derived (57) from terephthaUc acid [100-21-0] by amination of 1,4-cyclohexanedimethanol (30) [105-08-8], Endocyclization, however, competes favorably and results in formation of the secondary amine (31) 3-a2abicyclo[3.2.2]nonane [283-24-9] upon diol reaction with ammonia over dehydration and dehydrogenation catalysts (58) ... 

Ca.ta.lysts, A small amount of quinoline promotes the formation of rigid foams (qv) from diols and unsaturated dicarboxyhc acids (100). Acrolein and methacrolein 1,4-addition polymerisation is catalysed by lithium complexes of quinoline (101). Organic bases, including quinoline, promote the dehydrogenation of unbranched alkanes to unbranched alkenes using platinum on sodium mordenite (102). The peracetic acid epoxidation of a wide range of alkenes is catalysed by 8-hydroxyquinoline (103). Hydroformylation catalysts have been improved using 2-quinolone [59-31-4] (104) (see Catalysis). 

In mammals, dieldrin and endrin are also converted into keto metabolites (Figure 5.5). In the rat, the keto metabolite is only a minor product, which, because of its lipophilicity, tends to be stored in fat. With endrin, a keto metabolite is formed by the dehydrogenation of the primary monohydroxy metabolite. In mammals, the trans diol of dieldrin is converted into a diacid in vivo (Oda and Muller 1972). 

An alternative new synthetic approach to chrysene 1,2-dihydro-diol based on Method IV has recently been developed (60). This method (Figure 12) entails synthesis of 2-chrysenol via alkylation of 1-1ithio-2,5-dimethoxy-1,4-cyclohexadiene with 2-(1-naphthyl) e-thyl bromide followed by mild acid treatment to ge nerate the diketone 12. Acid-catalyzed cyclization of 12 gave the unsaturated tetracyclic ketone 13 which was transformed to 2-chrysenol via dehydrogenation of its enol acetate with o-chloranil followed by hydrolysis. Oxidation of 2-chrysenol with Fremy s salt gave chrysene... 

The metabolite but-3-ene-l,2-diol (10.104, Fig. 10.24) is of particular interest since further oxidation by alcohol dehydrogenase yields reactive products such as a,)3-unsaturated ketones [166] [167], Dehydrogenation of the primary alcoholic group to the a-hydroxyaldehyde followed by fast rearrange-... 

If a diol is oxidatively dehydrogenated to form a diacid via an intermediate with one Off group, then a first order plot based on hydrogen evolution can exhibit some curvature. This is because the slope at any time will reflect the instantaneous concentrations of the diol and intermediate as well as their intrinsic reactivities. First order plots for the reaction of ethylene glycol, 1,4-butanediol and diethanolamine are shown in Figure 2. All plots are reasonably linear, consistent with reaction via an intermediate with a rate constant rather similar to that of the starting diol (or a direct reaction with no intermediate whatsoever). 

Synthesis from Citronellol. Citronellol is hydrated to 3,7-dimethyloctan-l,7-diol, for example, by reaction with 60% sulfuric acid. The diol is dehydrogenated catalytically in the vapor phase at low pressure to highly pure hydroxydihydrocitronellal in excellent yield. The process is carried out in the presence of, for example, a copper-zinc catalyst [68] at atmospheric pressure noble metal catalysts can also be used [69]. 

The syn- and anfi-diol epoxides of benz[a] anthracene and benzo[a] pyrene have been prepared from dihydroarenes by sequential Prevost reaction with silver benzoate-iodine, dehydrogenation, methanolysis, and epoxidation, e.g.,... 

Ceric ammonium nitrate appears to be a valuable reagent for dehydrogenation of bisbenzylisoquinoline alkaloids. For example, oxidation of tetrandrine (48) with 8 mol of this reagent in buffered HOAc, followed by NaBH4 reduction of the intermediate imine 381, gave a 95% yield of diamine 382, as well as the crystalline diol 383. Similarly successful results were obtained with heman-dezine (24a) and O-methylmicranthine (384), the latter demonstrating that this procedure is compatible with secondary amino groups. Berbamine (364),... 

Optically active poly(silyl ether)s were also synthesized by asymmetric induction on the silicon atom from chiral diols or a chiral Rh catalyst [178]. In the dehydrogenative polycondensations of bis(silane)s and several chiral diols, the highest ee value of the silicon atom was 13.7%. In the polymerization of a bis(silane) and an achiral diol, however, the use of only 5 mol% of RhCl[(R)-BINAP] resulted in induction of 39.8% ee of the silicon atom (Scheme 45). 

As the proportion of benzene in the solvent was increased, dehydrogenation of dithioacetals was less pronounced and a-diol scission was more evident. 

Dehydrogenation of 1,4- or 1,5-diols to lactones. This Ru-catalyzed transfer dehydrogenation can be effected with high selectivity when the 2-position of 1 is... 

Oxidative cleavage of alkenes to carboxylic acids.1 Alkenes are oxidized to carboxylic acids by H202 (35%) catalyzed by H2W04 in a weakly acidic medium (pH 4-5) maintained by addition of KOH. The oxidation probably involves initial oxidation to a 1,2-diol followed by dehydrogenation to an a-ketol, which is then cleaved to a mono- or dicarboxylic acid. 

Compound 85 was dehydrogenated at 300° over palladium black under reduced pressure to a pyridine derivative 96 which was independently synthesized by the following route. Anisaldehyde (86) was treated with iodine monochloride in acetic acid to give the 3-iodo derivative 87. The Ullmann reaction of 87 in the presence of copper bronze afforded biphenyldialdehyde (88). The Knoevenagel condensation with malonic acid yielded the unsaturated diacid 91. The methyl ester (92) was also prepared alternatively by a condensation of 3-iodoanisaldehyde with malonic acid to give the iodo-cinnamic acid (89), followed by the Ullmann reaction of its methyl ester (90). The cinnamic diester was catalytically hydrogenated and reduced with lithium aluminium hydride to the diol 94. Reaction with phosphoryl chloride afforded an amorphous dichloro derivative (95) which was condensed with 2,6-lutidine in liquid ammonia in the presence of potassium amide to yield pyridine the derivative 96 in 27% yield (53). 

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