Starting materials and reagents

A -Acetyltyrosine methyl ester (400 mg, 1.68 mmol) and 3,5-dichloro-l-fluoropyridinium triflate (lm 632 mg, 2 mmol) were stirred under N2 in dry CH2Cl2/MeCN (10 mL, 9 1). After 8 h the starting material and reagent were consumed. The reaction mixture was poured into H20 (10 mL), neutralized with NaHC02, and separated. The organic layer was washed with H20 (10 mL), dried (Na2S04) and concentrated under reduced pressure. The crude product was purified by vacuum column chromatography (silica gel, 60% EtOAc/petroleum ether, bp 35-60 JC) yield 280 mg (65%). 

Notably, SVO can display a variety of phases, both stoichiometric and nonstoichiometric. Thus, variations in reaction conditions, starting materials, and reagent stoichiometries for the preparation of SVO can result in a wealth of products that display different structures and different properties. In addition, the variety of oxidation states available to the silver and especially the vanadium components of SVO, plus the open structure of some of the SVO materials, suggest that these materials are well suited for electron transfer applications. It is thus logical and not surprising that reports of SVO battery applications and SVO redox catalyst applications appear within similar time frames. Some reports involving the structure of SVO solids and the catalysis of organic substrate oxidation by SVO-based catalysts will be described in Section 13.2, due to their possible relevance to the SVO battery chemistry described in Section 13.3. 

The electron-rich oxygen atom of a secondary amide derivative of cinnamic acid can be as effective as that of a cinnamyl ether or alcohol in directing anr/-Michael additions to some amide Michael acceptors. For example, BuLi adds to the amide 51 to give a 90 10 ratio of anti-Michael Michael addition products 52 53.31 With the alkyne54 the effect is even more pronounced MeLi gives solely the anti-Michael product 55. These reactions are however very sensitive to starting material and reagent structure. 

Logically, it makes sense that optically inactive reagents and catalysts cannot form optically active products. If the starting materials and reagents are optically inactive, there... 

What has made this all possible is that chemists have learned how to understand the selectivity of radical reactions to such a degree that they can design starting materials and reagents to define... 

To carry out synthesis we must think backwards. We examine a compound and ask What starting material and reagent are needed to make it If we are using nucleophilic substitution, we must determine what alkyl halide and what nucleophile can be used to form a specific product. This is the simplest type of synthesis because it involves only one step. In Chapter 11 we will learn about multistep syntheses. 

Suppose, for example, that we are asked to prepare (CH3)2CHCH20H (2-methyl-l-propanol) from an alkyl halide and any required reagents. To accomplish this synthesis, we must fill in the boxes for the starting material and reagent in the accompanying equation. 

When we first introduced the concept of enantiomers and chirality in Chapter 16, we stressed that any imbalance in enantiomers always derives ultimately from nature. A laboratory synthesis, unless it involves an enantiomerically pure starting material or reagent, will always give a mixture of enantiomers. Here is just such a synthesis of the Japanese beetle pheromone you have just met. You can see the Z-selective Lindlar reduction in use—only one geometrical isomer of the double bond is formed— but, of course, the product is necessarily racemic and therefore useless as beetle bait, because in the original addition of the lithiated alkyne to the aldehyde there can be no control over stereochemistry. If all the starting materials and reagents are achiral, the product must be... 

Crafts process is to generate carbonium ions from the alkyl or acyl halides. It would be expected, then, that a number of other combinations of starting materials and reagents which lead to carbonium ions should be capable of effecting acylation or alkylation. Indeed we find that olefins (p. 35), alcohols (p. 36), ethers (p. 36), and esters (p. 37) can be used as starting materials for aromatic alkylation reactions in the presence of such catalysts as boron trifluoride, sulfuric acid, or anhydrous hydrogen fluoride.69 Acylations can be carried out with acids (p. 37),64 acid halides (p. 230), and acid anhydrides (p. 37). The Fries reaction65 (in which phenolic esters are converted to hydroxy aromatic ketones by means of aluminum chloride) appears to be an example of a typical acylation reaction in which the ester itself acts as the source of an acyl carbonium ion ... 

Usually cost estimates include the cost and equivalents of starting materials and reagents, yields of products of acceptable quality, and total kilos of intermediates required per kilo of product. Other factors that may be considered include... 

Equipment Clean thoroughly Rinse with polar solvents and flush equipment thoroughly Azeotrope dry Monitor moisture before charging starting materials and reagents... 

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