Catalysts reactions with diols

Trickle bed reaction of diol (12) using amine solvents (41) has been found effective for producing PDCHA, and heavy hydrocarbon codistiUation may be used to enhance diamine purification from contaminant monoamines (42). Continuous flow amination of the cycloaUphatic diol in a Hquid ammonia mixed feed gives >90% yields of cycloaUphatic diamine over reduced Co /Ni/Cu catalyst on phosphoric acid-treated alumina at 220°C with to yield a system pressure of 30 MPa (4350 psi) (43). 

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) ... 

Diols yield acetonides, even in the presence of a 17oc-hydroxylgroup. Reaction with acetone in the presence of zinc chloride as catalyst leads to the formation of diacetone alcohol acetal as a by-product. ... 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

Deprotonaiion of the intermediate by reaction with water yields the neutral gem diol and regenerates the acid catalyst. 

Quinoxalines 85 have been prepared by the reaction of diols with benzene-1,2-diamines in the presence of a ruthenium catalyst <06TL5633>. Iodobenzene diacetate has been suggested as a less toxic alternative to lead tetraacetate for the oxidative cyclisation of iminooximes to quinoxaline iV-oxides 86 <06TL4969>. 

The formation of molybdenum complexes with diols (formed by olefin oxidation) was proved for the use of the molybdenum catalysts. Therefore, the participation of these complexes in the developed epoxidation reaction was assumed [242]. 

The Lewis acid catalyst 53 is now referred to as the Narasaka catalyst. This catalyst can be generated in situ from the reaction of dichlorodiisopropoxy-titanium and a diol chiral ligand derived from tartaric acid. This compound can also catalyze [2+2] cycloaddition reactions with high enantioselectivity. For example, as depicted in Scheme 5-20, in the reaction of alkenes bearing al-kylthio groups (ketene dithioacetals, alkenyl sulfides, and alkynyl sulfides) with electron-deficient olefins, the corresponding cyclobutane or methylenecyclobu-tene derivatives can be obtained in high enantiomeric excess.18... 

The curing reaction can be carried out thermally or with the addition of a catalyst. The thermal cure is strongly influenced by impurities associated with the synthesis. The greater the degree of monomer purity, the more slowly the thermal cure proceeds. If the monomer is sufficiently purified, the cure rate can be predictably controlled by the addition of catalysts. As with the aromatic cyanate esters, the fluoromethylene cyanate esters can be cured by the addition of active hydrogen compounds and transition metal complexes. Addition of 1.5 wt% of the fluorinated diol precursor serves as a suitable catalyst.9 The acetylacetonate transition metal salts, which work well for the aromatic cyanate esters,1 are also good catalysts. 

A number of optically active 1,1 -binaphthyl compounds, 8168 and 9,169 have been prepared with a view to use them as asymmetric catalysts. Compounds 8 (X = Br and OTf)170,171 and 9 [R3 = Me(OTf)2]169 have been used to resolve diols in their reaction with benzoyl chloride. Tin hydrides based on structure 8 (X2 = MeH,172 Bu H,173 and Me3CCH2H171) have been designed for carrying out enantioselective reductions. 

The same group also demonstrated an efficient, two-step asymmetric synthesis of (S)-2-phenylpiperidine as an extension of the N-heterocycUzation of primary amines with diols the results are illustrated in Scheme 5.25. First, the reaction of enantiomerically pure (R)-l-phenylethylamine and 1-phenyl-1,5-pentanediol was conducted to produce a diastereomeric mixture of the corresponding N-(l-phenyl-ethyl)-2-phenylpiperidines 32 and 33 with 92% diastereomeric excess (de). Hydrogenation of this diastereomeric mixture of 32 and 33 with Pd/C catalyst then gave (S)-2-phenylpiperidine in 96% yield (78% ee). 

The iridium-catalyzed reaction of primary amines with diols gave cyclic amines. The reaction of amine 109 with diol 110 in the presence of [Cp lrCl2]/NaHC03 catalyst gave heterocyclization product 111 (Equation 10.26) [50]. 

The starting diol was transformed into the dibromide by elemental bromine with triphenyl phosphine adduct which undergoes the Arbuzov-Michaelis reaction under somewhat drastic conditions at 150 °C (step a). Catalytic removal of the benzyl group was performed by a Pd/C catalyst (step b) and the alcohol formed was allowed to react with dichloropurine in the presence of triphenylphosphine and diethylazodicarboxylate (Mit-sunobu reaction) (step c). Finally the desired product was obtained by reaction with methylamine (step d) and the removal of ethyl groups at the phosphorus centre was performed by transilylation using trimethyliodosilane (step e). 

As with the Diels-Alder reaction, it is possible to achieve enantioselective cycloaddition in the presence of chiral catalysts.89 The Ti(IV) catalyst C with chiral diol ligands leads to moderate to high enantioselectivity in nitrone-alkene cycloadditions.90... 

The Rawal group next applied diol catalysis to the enantioselective vinylogous Mukaiyama aldol (VMA) reaction of electron-deficient aldehydes [105]. Screening of various known chiral diol derivatives, including VANOL, VAPOL, BINOL, BAMOL, and TADDOL, revealed that 38a was the only catalyst capable of providing products in acceptable levels ofenantioselection (Scheme 5.55). Subsequent to this work, Scettri reported a similar study of TADDOL-promoted VMA reactions with Chan s diene [106]. 

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]. 

---