Yield, of intermediate

For the consecutive reactions A B C, a higher yield of intermediate B is obtained in batch reac tors or PFRs than in CSTRs. 

Yield of intermediate versus fraction conversion for k"/k" = 5. Upper curve ri = 1 lower curve r < 0.3. 

The conclusion is that no unevolved star shows the composition of evolved RGB stars, but rather one similar to that predicted for yields of intermediate-mass AGB stars (IM-AGB see [8]). However, since dilution with material not contaminated by CNO burning could explain the observed trends for C and N, we have to dig deeper. 

Substituted pyridinium salts of this nature were difficult to obtain by other methods. This sequence is initiated with condensation of the anions of imine 50 with malonaldehyde monoacetals 51 to access glutaconaldehyde monoacetals 52. The monoacetal-aldehyde was then reacted with primary amines ( -BuNH2) to give 3-substituted pyridinium salts 49. When the silylimino derivative (R1=Si(CH3)3) was used, substantially higher yields of intermediate glutaconaldehydes were obtained. 

Figure 16.6 When reaction rate is very high, zones of nonhomogeneity exist in a reactor. This condition is detrimental to obtaining high yields of intermediate R from the reactions...

For reactions in series the BFB always gives a lower yield of intermediate compared to a fixed bed. 

A recent literature report described a green procedure for the condensation of arylacetonitriles with cyclic ketones using phase-transfer catalysis. This process was applied to the synthesis of venlafaxine, which was realized in overall 30% yield in two steps from commercially available 14. The condensation step was run in aqueous sodium hydroxide in the presence of tetrabutylammonium sulfate, to provide quantitative yield of intermediate 15. Hydrogenation in a formalin-methanol mixture provided the final product venlafaxine (1) in 30% overall yield. This protocol did not necessitate intermediate purification steps, making it attractive from the commercial standpoint. 

Figure 1. A schematic representation of a membrane reactor for improving yields of intermediate products in a partial oxidation reaction.

Indole substituent Yield of intermediate (%) Yield of indole (%) Ref. 

A further difference between CSTR batteries and PFRs is that of product distributions with complex reactions. In the simple case, A- B- C for example, a higher yield of intermediate product B is obtained in a PFR than in a single CSTR. It is not possible to generalize the results completely, so that the algebra of each individual reacting system must be worked out to find the best mode. 

Scheme 8 shows the synthetic routes of the oxadiazole unit containing phospho-nium salt monomers and Scheme 9 outlines the preparation of Jt-conjugated polymers composed of oxadiazole units [67]. The synthetic pathways to the para-linked salt monomer (A) and meta-linked salt monomer (B) are of multisteps, but the synthetic method for each step is not difficult and the product yields of intermediate compounds are very high (75-95%). Treatment of bis(4-methylphenyl)hydrazine with POCl3 results in the formation of the 2,5-bis(4-methylphenyl)-1,3,4-oxadiazole. 

For a 10% improvement in yield of Intermediate F in Step 2, in manufacturing 100 tonnes per annum of FCP1, provided the product is sold at the same price and the plant capacity that is released can be filled, the total savings are ... 

The de novo discovery synthesis of capecitabine (1) was reported by the Nippon Roche Research Center scientists9,19 and was followed up with a preparation invented by a team at the Hoffinann-La Roche laboratories in New Jersey for the conversion to 1 from 5 -DFCR (10).2° In the first route, 5-fluorocytosine (15) was mono-silated using one equivalent of hexamethyldisilazane in toluene at 100 °C followed by stannic chloride-catalyzed glycosidation with known 5-deoxy-l,2,3-tri-0-acetyl-p-D-ribofuranoside (17) in ice-cooled methylene chloride. While this procedure provided the 2, 3 -di-0-acetyl 5-fluorocytidine 18 in 76% yield on a 25-g scale, an alternative method was also devised using in situ-generated trimethylsilyl iodide in acetonitrile at 0°C to provide a 49% yield of 18 on smaller scale. Acylation of the N -amino group of the bis-protected 5 -DFCR derivative was accomplished by the slow addition of two equivalents of -pentyl chloroformate to a solution of 18 in a mixture of pyridine and methylene chloride at -20 °C, followed by a quench with methanol at room temperature to provide the penultimate intermediate 19 on 800-g scale. The yield of intermediate 19 was assumed to be quantitative and was subjected to the final deprotection step, with only a trituration to... 

Anthranilic acid derivatives 1 react readily with alkali cyanates to give good yields of intermediate 2-ureidobenzoic acids or alkyl 2-ureidobenzoates which, without being isolated, sometimes easily cyclize on heating with acid or alkali to give the respective quinazoline-2,4(li/,3//)-... 

Example 1. The isothermal van de Vusse (1964) reaction involves four species for which the objective is the maximization of the yield of intermediate species B, given a feed of pure A. The reaction network is given by... 

Example 4 Here, we revisit the van de Vusse reaction of Example 1 with altered rate constants. The objective function again is the yield of intermediate species B. The rate vector is given by R X) = [-X X, — 2X, 2X, ... 

Figure 5. Fractional yields of intermediates for the E2AdE3 model (0.5M 1-propanol reactant/ 5mM sulfuric acid catalyst at 375 C/ 34.5 MPa).

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