Step 2 Product Group Selection

The starting point for upper management to tangibly show their support is to help you choose the product group that you will focus on. All materials that you purchase should be divided into groups based on similar characteristics. Examples would be solvents, salts, coatings, or ductwork. 

Under the existing purchasing process these materials may be coming from a wide variety of different suppliers. 

A report should be prepared showing the pounds or number purchased and dollars spent in each area by material and total. The annual purchases made in each group should be calculated. This shows where the largest purchases are. A Pareto analysis can be prepared on the annual purchases. The area that can produce the most return will be obvious from the Pareto analysis. This process will be discussed in Chapter 12. 

The aimual use figures need to be broken down by location in a multiplant operation. All loeations must be eonsidered in the seleetion process. Long-range plans from upper management must be ineluded in this step so that the chosen supplier is able to grow with the plan. New produets and ventures that are planned need to be eonsidered as the suppliers are ehosen. 

A report on the group seleeted should eonsist of volumes and dollars by supplier for each location for a multi-plant situation as well as totals by supplier. This doeument becomes the starting point for the analysis of the current proeess and where improvements ean and need to be made. 

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The syntheses in Schemes 13.45 and 13.46 illustrate the use of oxazolidinone chiral auxiliaries in enantioselective synthesis. Step A in Scheme 13.45 established the configuration at the carbon that becomes C(4) in the product. This is an enolate alkylation in which the steric effect of the oxazolidinone chiral auxiliary directs the approach of the alkylating group. Step C also used the oxazolidinone structure. In this case, the enol borinate is formed and condensed with an aldehyde intermediate. This stereoselective aldol addition established the configuration at C(2) and C(3). The configuration at the final stereocenter at C(6) was established by the hydroboration in Step D. The selectivity for the desired stereoisomer was 85 15. Stereoselectivity in the same sense has been observed for a number of other 2-methylalkenes in which the remainder of the alkene constitutes a relatively bulky group.28 A TS such as 45-A can rationalize this result. 

The phosphitylation reaction (step a) and sulfurization leading to the corresponding thiophosphate (step b) proceeded under standard conditions. After deprotection (step c) and selective introduction of the DMTr group (step d) no transphosphorylation 2 3 was noted. This fact can be explained by the steric factor combined with the lower activity of thiophos-phates in comparison with normal phosphates. This enabled further phosphitylation (step e) by the customary phosphoroamidites. A difficulty in Se-kine s procedure is that the phosphitylating reagent must be prepared in situ and has relatively low purity. Luckily the by-products formed are inert tetra-coordinate species. 

The allylic sulfonyl allene 35, possessing unsymmetrical substitution at the distal double bond of the allene, was examined. Since there are two possible sites for y5-hy-dride eliminahon, a variety of isomers are possible. Treatment of allene 35 with [Rh(CO)2Cl]2 gave a 3 5 1 raho of the three possible products 36, 37, and 38, which translates into an 8 1 constitutional group selectivity in the y5-hydride elimination step ((364-37) 38) and an T/Z-selechvity of 1 2 (Tab. 8.8, entry 1). 

This product is formed because the green OH group leaves more readily than the black because the carbocation stabilized by two phenyl groups forms more readily than the carbocation stabilized by two alkyl groups. The migration step follows without selectivity as both alkyl groups on the black alcohol are the same. 

Although the subsequent discussion describes the stereoselection at the steady state through the example of radical reactions, the analysis and principles are general for any reaction profile that fits into the scheme of complex stereoselective reactions. In the process proposed and analyzed by Curran et al., the activation of compounds of type 1 is done, for example, by radical formation. The group selectivity in this first step has again no effect on the stereomeric nature of the product. To obtain a stereoconvergent process it is crucial, however, that the reaction is operating at the steady state. This means that the concentrations of the radial intermediates (compounds in brackets in Scheme 2) is low and stationary, while their absolute concentrations are determined by the different rates of reaction. 

The key step is the selective C—H bond activation of two methyl groups of an ortho-tert-hutyl in the Schiff base 434. Treatment of 434 with Pd(OAc)2 afforded the palladacycle 435 in 75 % yield by the help of rather strong coordination to N and O functions. The first functionalization was achieved by the reaction with the alkenylboronic acid to yield the alkylated product 436 in 86 % yield, which was converted to 437 by the Friedel-Crafts reaction. Then the second palladacycle formation from 437 provided two diastereomers 438, which were, without isolation, subjected to carbonylation (40 atm) at room temperature. Treatment of crude reaction mixture with silica gel cleaved the Schiff base and spontaneous lactonization occurred to give a mixture of the lactones 439 and 440 (6 1). The main product was N-alkylated to yield 441. Finally, the fourth ring was constructed by a Heck-type reaction on the aromatic ring to give the desired compound. 

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