Catalytic yield

The reason that OH does not attack the u-carbon in 63, in contrast to the reaction in Eq. (17), would be due to the stronger electron donation by the /3-carbon in 63, which increases the electron density at the a-carbon atom. Addition of ethylene glycol vinyl ether to the p-toluenesulfonate salt of 64 in CDC13 catalytically yields 2-methyl-1,3-dioxolane (Eq. (18)). The reaction proceeds almost instantaneously, and a 50-fold equivalent of the substrate is completely converted to 2-methyl-1,3-dioxolane, which was confirmed by -NMR. After the reaction, the Pt(III) dimer complex without alkyl ligand is left in the solution, which is still capable of catalysis. The reaction is shown as Eq. (18). 

Varieties of primary and secondary alcohols are selectively oxidized to aldehyde or carbonyl compounds in moderate to excellent yields as summarized in Table 3. As can be seen, /(-substituted benzyl alcohols (e.g., -Cl, -CH3, -OCH3, and -NO2) yielded > 90% of product conversion in 3-4 h of reaction time with TOP in the range of 84-155 h (entries 2-5, Table 3), Heterocyclic alcohols with sulfur- and nitrogen-containing compoimds are found to show the best catalytic yield with TOP of 1517 and 902 h for (pyrindin-2-yl)methanol and (thiophene-2-yl) methanol, respectively (entries 9 and 10, Table 3). Some of aliphatic primary alcohols (long chain alcohols) and secondary alcohols (cyclohexanol, its methyl substituted derivatives and norboman-2-ol) are also selectively oxidized by the membrane catalyst (entries 11-14 and 15-17, Table 3) with TOP values in the window of 8-... 

Fig. 56. Catalytic yield as a function of the partial pressure ratio p0l lpco for flat and stepped Pt(] 11) surfaces (151).

Intermolecular asymmetric aminations are at an early stage of development, and consequently much lower turnover frequencies and catalytic yields have been observed at this stage. In the example shown, a key aspect is the activation of the iridium complex catalyst by fluoride ion [111] (Scheme 38). 

Quinazolines 14, especially those bearing no substituents at position 4, are reduced to 3,4-dihydroquinazolines 15 by various reducing agents, e.g. sodium borohydridc," - or sodium in tetrahydrofuran, ° or catalytically. - yields obtained by catalytic hydro-... 

In the case of heterogeneous high yield catalysts, Thiele modulus criterion would predict an appreciable broadening of MWD in comparison to traditional catalysts (higher values). This broadening could be also due to a notable enlargement of the polymer particle and, therefore, to an increase in the Thiele modulus in proportion to catalytic yield... 

The effect of the first parameter has been discussed in a previous paper [4]. In this paper, we investigate the effect of the other two parameters. Once it is possible to set the A/B complex ratio by tuning the synthesis conditions during the ion exchange procedure, the next step is to relate this ratio to catalytic yield and/or selectivity of the resulting heterogeneous Cu(II)-catalyst. 

Contrary to the reduction of other monocyclic 1,2,3-triazines (see Section 2.1.2.4.1.) reduction of 4,5,6-triphenyl-l,2,3-triazine with zinc in acetic acid (or catalytically) yielded 3,4,5-triphenylpyra-zole.88 The same compound was obtained when 4,5,6-triphenyl-l,2,3-triazine was treated with nonacarbonyldiiron.260... 

Whilst metal centres have provided the majority of known catalytic sites in MOFs, organic units have also provided a number of compelling examples. The size-selective catalytic activity of POST-1, described in Sections 1.2.1.1.2 and 1.2.3.2, in the transesterification of alcohols is attributed to the presence of unprotonated pyridyl groups that project into the channels and which likely assist in the deprotonation of the alcohol reactants. Catalytic yields in excess of 77 % were achieved with an ee = 8 % using this homochiral system. 

Fig. 10 Comparison of catalytic yields of methyl lactate for the conversirai of hexose-based sugars in methanol with different heterogtaieous catalysts. CSM = carbon silica cmnposite. Conditions 160°C, 20 h, 22.5 mgs gar mL, 16 mgcj,aiys, mL (slightly different fin CSM respectively 155°C, 30 and 21 mg mL ) All craiversions >95%. Data liom [66,107, 125]...

Example 21-2. Effect of Kind of Stock on Catalytic Yields. Example 21-1 will be repeated except to consider an 11.7 Characterization Factor stock which was produced by viscosity breaking. 

Table 21-9. Material Balance of Catalytic Yields (Examples 21-1 and 21-3) Basis 100 gallons...

In a single stage, without liquid recycle, the conversion can be optimized between 60 and 90%. The very paraffinic residue is used to make lubricant oil bases of high viscosity index in the range of 150 N to 350 N the residue can also be used as feedstock to steam cracking plants providing ethylene and propylene yields equal to those from paraffinic naphthas, or as additional feedstock to catalytic cracking units. 

Sometimes a large proportion of sulphuric acid is employed (see below under esters of dibasic acids). The good yields thus obtained are partially due to the removal of water by the acid as well as to the catalytic effect. 

Oxidation of benzoin with concentrated nitric acid or by catalytic amounts of cupric salts in acetic acid solution, which are regenerated continuously by ammonium nitrate, yields the diketone benzil ... 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

A mixture of an acid anhydride and a ketone is saturated with boron trifluoride this is followed by treatment with aqueous sodium acetate. The quantity of boron trifluoride absorbed usually amounts to 100 mol per cent, (based on total mola of ketone and anhydride). Catalytic amounts of the reagent do not give satisfactory results. This is in line with the observation that the p diketone is produced in the reaction mixture as the boron difluoride complex, some of which have been isolated. A reasonable mechanism of the reaction postulates the conversion of the anhydride into a carbonium ion, such as (I) the ketone into an enol type of complex, such as (II) followed by condensation of (I) and (II) to yield the boron difluoride complex of the p diketone (III) ... 

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

If one heats acetone and pyrrole in the presence of catalytic amounts of acid, so-called acetone pyrrole is formed in over 80%i yield. This colorless, macrocyclic compound contains four pyrrole units which are connected by dimethylmethylene bridges, ft is formed by electrophilic-a-substitution of pyrrole by acetone, acid-catalyzed oligomerization, and spontaneous. 

---