Starting materials, requirements for

Hhat Is the starting material required for a Claisen-Cope route to (31) ... 

The starting materials required for preparing the 2,3-disubstituted tetrahydronaphthalenes were 5,6,7,8-tetrahydro-2-naphthol (obtainable from tetrahydronaphthalene) and methyl 3-hydroxy-2-naphthoate, which was reduced to the known tetrahydro ester (Vc) and the latter saponified to the known tetrahydroacid. 

Answer The structures of the starting materials required for procedure IX-7 can be deduced by cleaving the bond... 

If the above precautions are insufficient to produce the purity required, the starting materials required for the quatemisation reaction should be purified by distillation and/or the methods of purification outlined in Purification of Laboratory Chemicals by Armarego and Chai [135], It should be noted that the starting materials often degrade over time and therefore these purification techniques should be employed immediately before the quatemisation reaction is undertaken. 

To address these problems, a fluorous tag was appended to the catalyst (48) [12c], which reduced the separation to an ordinary filtration through a pad of fiuorous silica gel that retained the catalyst, whereas the product was eluted. Subsequent change of the solvent resulted in elution of the catalyst that could be reused. The classical chromatography of the crude mixture after the workup was thus avoided. The presence of the fiuorous tag had practically no effect on the catalytic activity (Table 4.11 compare entries 1 with 3 5) [12c]. However, the polyfiuorinated starting material required for the synthesis of 48 and the fiuorous silica gel are rather expensive, which may become prohibitive for large scale applications therefore, other options were also explored. 

Of these, the thermal synthesis of [NF4][SbF6] " is most convenient (Synthesis A) and provides the starting material required for the synthesis of other [NF4] salts by indirect methods. For the synthesis of pure [NF4] salts on a small scale, low-temperature UV photolysis is preferred (Synthesis B). ... 

This consists of obtaining the necessaiy information regarding the specific application of the labelled compound. Careful consideration must be given to the different synthesis procedures (laboratory, pilot, industrial) that can be applied to obtain the final product as well as to the availability of the intermediate non-labelled compounds, their specifications and purity. Also, analytical data, such as chromatography results for intermediate and final compounds, must be collected. The labelling position and starting material must then be chosem This preliminary step also establishes the amount of starting material required for the final synthesis. 

You wish to prepare approximately 50 g of Si02 by the sol-gel process under the following conditions You start with a solution of 50 mol% TEOS in ethanol and you add 10 mol of H2O per mole of aUcoxide. Determine the volume of each starting material required for the process, assuming that the reaction goes to completion. 

The polymer is exposed to an extensive heat history in this process. Early work on transesterification technology was troubled by thermal—oxidative limitations of the polymer, especially in the presence of the catalyst. More recent work on catalyst systems, more reactive carbonates, and modified processes have improved the process to the point where color and decomposition can be suppressed. One of the key requirements for the transesterification process is the use of clean starting materials. Methods for purification of both BPA and diphenyl carbonate have been developed. 

There will be a continued need for enantiospecific methods of preparation and analysis, not only to ensure the quality of the final drug substance and reference materials, but also to control starting materials used for their manufacture, and key intermediates during synthesis. Likewise, specific and sensitive bioanalytical methods will be required to follow the fate of individual enantiomers after their administration. 

In terms of mass, it therefore requires less starting materials (chemicals) for its own production. 

The most convenient and economic techniques of choice for the rapid analysis of starting materials and for the assessment of purity of a crude reaction product are t.l.c. and g.l.c. These techniques may also be used to monitor the progress of a reaction for which optimum conditions are uncertain, as may be the case when an established published procedure is used as the basis for carrying out other preparations of a similar nature. In these cases the reaction is monitored by the periodic removal from the reaction mixture of test portions for suitable chromatographic study. Clearly the chromatographic behaviour of starting materials and, if possible, expected products, needs to be established prior to the commencement of the reaction. For t.l.c. this would include solvent and thin layer selection, a detection method, and an appraisal of sensitivity of detection with respect to the concentration of components in the reaction medium. For g.l.c. preliminary experiments would be required to select a suitable column and the appropriate operating conditions. 

Tricyclic pyrrole derivative 2.43 is a drug currently under development for the treatment of schizophrenia. It is prepared by a Knorr pyrrole synthesis. What are the structures of the two starting materials required, and that of the intermediate enamine ... 

How can X-b be broken up so that the required starting materials needed for procedure X-5 can be discerned ... 

Note that cleavages 2 and 3 require the same starting materials thus for this particular problem there are only I wo ways of forming XI a using procedure XI-4. To decide... 

Having established the three-dimentional structure of carbocations as planar, we can now study the stereochemical progression of Sk 1 reactions as compared to Sk2 reactions. As shown in Scheme 5.6, the stereochemical course of an Sk2 reaction is well defined because nucleophilic displacement of a leaving group proceeds with inversion of stereochemistry. Thus, the stereochemical outcome is defined by the stereochemistry of the starting material. As for SnI reactions, since the step required for initiation of these reactions involves formation of a planar species, incoming nucleophiles have equal access to both sides of the reactive carbocation. As shown in Scheme 5.7, this results in complete elimination of... 

Metal aUcoxides and alkyls are useful starting materials, particularly for the preparation of some unsolvated P-diketones that require anhydrous conditions (see Section 3.3). Addition of /3-diketonate ligands to metal alkoxides has also been used to produce heteroleptic metal complexes that are less reactive than the homoleptic metal alkoxides this simplifies the use of such complexes in chemical vapor deposition applications. ... 

The blending process requires scale tanks and meters to proportion the starting materials accurately for each type of product. The blend tanks should be equipped with agitators and heating devices to ensure uniform blend of products. Nitrogen blanketing also should be provided to protect the oil from oxidation. 

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