Limiting reagents worked example

The first reported example of enantioselective reductive amination was that of Blaser et al. at Solvias (Scheme 7.7) [2]. At the time, 1999, they were still tweaking the industrial process for metolachlor, the active ingredient of the herbicide Dual , and examined its synthesis via the reductive amination of methoxyacetone with 2 methyl 5 ethyl aniline (MEA, limiting reagent). Working at the 100 mmol scale, they showed that a very low loading of an Ir xyhphos complex, under 80 bar (1160 psi) H2, neat, 50 °C, and 14 h, were optimal. By doing so, a 76% ee with full conversion was achieved. 

The formation of macrocyclic ligands by template reactions frequently involves the reaction of two difunctionalised precursors, and we have tacitly assumed that they react in a 1 1 stoichiometry to form cyclic products, or other stoichiometries to yield polymeric open-chain products. This is certainly the case in the reactions that we have presented in Figs 6-8, 6-9, 6-10, 6-12 and 6-13. However, it is also possible for the difunctionalised species to react in other stoichiometries to yield discrete cyclic products, and it is not necessary to limit the cyclisation to the formal reaction of just one or two components. This is represented schematically in Fig. 6-19 and we have already observed chemical examples in Figs 6-4, 6-11 and 6-18. We have already noted the condensation of two molecules of 1,2-diaminoethane with four molecules of acetone in the presence of nickel(n) to give a tetraaza-macrocycle. Why does this particular combination of reagents work Again, why are cyclic products obtained in relatively good yield from these multi-component reactions, rather than the (perhaps) expected acyclic complexes We will try to answer these questions shortly. 

The reported 2731 yield of adamantanone oxime from this reaction (63 %) is misleading since it is based on Cl2 as the limiting reagent. Careful product analyses have shown that the overall ratio of tertiary to secondary substitution products ( 2) is quite normal275), While this reaction is clearly much less useful for the preparation of methylene substituted adamantanes than the ionic processes discussed above, it may be applicable in more specialized cases such as, for example, the synthesis of polyalkylsubstituted adamantanones where the ionic processes work poorly. 

Common immunochemical assay formats to select from include the 96-well microtiter plates, dipsticks, coated test tubes, and membrane-based flow through devices. If the end-user is a trained technician working in a well-equipped laboratory and needs to detect and tentatively identify, for example, antimicrobial residues in hundreds of meat samples per day, a multiwell or other high-through-put format should be chosen. If, on the other hand, the end user is a quality control inspector at a milk factory who has limited time to find out whether the penicillin residues in the milk waiting to be unloaded exceed a certain level, the same reagents used in the first instance may require a more user-friendly format such as dipstick or membrane-based flow through device. 

Although limited, the examples in this work using tris(diethylamino)phosphanc suggest many other potential applications for this readily available reagent. ... 

Due to limited space, this section will focus on the fundamental aspects of fluorinated organometallic species, and limit the discussion to examples that illustrate these issues. These authors have recently published two comprehensive reviews of fluorinated aliphatic and un-saturated organometallic reagents and the reader will frequently be referred to these sources for more detailed information. An effort has been made to include work published after these reviews. 

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