Reagents for preparation

Section 20 6 Acid anhydrides are less reactive toward nucleophilic acyl substitution than acyl chlorides but are useful reagents for preparing esters and amides... 

Wittig reagent for preparation of (9,0-d ichloro-/>-dim ethylamino-styrene, 46,33... 

Wittig reagent, for preparation of 1,4-di-phenyl-1,3-butadiene, 40, 36 for preparation of methylenecyclo-hexene, 40,66... 

The combination of copper salts and snlfnric acid is another widely used charring reagent. For preparation, 10 ml of concentrated H2SO4 has to be mixed carefully with 90 ml of acetic anhydride. Three grams of copper-II-acetate is dissolved in 100 ml of 8% phosphoric acid. After plate dipping or plate spraying, 15 min of heating at 125°C is recommended [17]. 

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

Because mercury is easily reduced, dialkylmercury compounds are useful reagents for preparing a large number of alkyls of other metals by group transfer reactions. This is illustrated by the following equations ... 

D. P. Curran, S. Hadida, S. Y. Kim, Tris(2-Perfluorohexyl-ethyfltin Azide A New Reagent for Preparation of 5-Substituted Tetrazoles from Nitriles with Purification by Fluorous Organic Liquid-Liquid Extraction , Tetrahedron 1999, 55, 8997. 

FIGURE 7.19 Reagents for preparing A-protected amino-acid fluorides,55-5661 Boc2-amino-acid fluorides (CyNF),58-59 and a nonbasic acid scavenger (BSA).62 CyNF = cyanuric fluoride DAST = diethylaminosulfur trifluoride TFFH = tetramethylfluoroformamidinium hexafluo-rophosphate BSA = b (trimethylsilyl)acetimide. 

Formylation and acetylation of a primary alkyl bromide.2 Detailed directions are available for preparation of disodium tctracarbonylferratesesquidioxanate, Na2Fe(CO)4(dioxanc), 5 (1), and for use of the reagent for preparation of aldehydes and ketones from alkyl bromides. 

Diphenylcyclopropenone has proved to be a useful synthetic reagent for preparing indolizines.91 It reacts readily with pyridine to give the indolizine 79 in 50% yield, and the yields of cyclized compounds tend to be greater when pyridazines and pyrazines are used instead of pyridines to give azaindolizines. 

The reagent for preparation of the methyl ester is added in ether solution. In pure form it is a yellow gas (bp -23 C) and highly explosive... 

The reagent can also be converted into 3-trimethylsilyl-1,3-bis-(ptaenyl-seleno)propene (2), a useful reagent for preparation of silyl enones. 

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