Fischer protocol

This dendritic support (1) was used to generate a library of indole derivatives with three centers of diversity following the Fischer protocol and the split and mix strategy. One example of this sequence is outlined in Scheme 7.1. 

The application of double Fischer indolization has been demonstrated to provide larger amounts of the indolocarbazole 4 from the treatment of the hisphenylhydra-zone 151 with aqueous sulfuric acid (63JCS2504). A considerably more efficient protocol has been devised by Robinson, who obtained 4 in 35% yield on treatment of 1,4-cyclohexanedione bisphenylhydrazone (151) in a mixture of acetic acid and sulfuric acid (63JCS3097). In spite of many recent developments, this is still the method of choice for the preparation of the parent system 4 as the starting materials are cheap and readily available. Cyclization of 151 in ethanol-water containing... 

The electrophilic carbene carbon atom of Fischer carbene complexes is usually stabilised through 7i-donation of an alkoxy or amino substituent. This type of electronic stabilisation renders carbene complexes thermostable nevertheless, they have to be stored and handled under inert gas in order to avoid oxidative decomposition. In a typical benzannulation protocol, the carbene complex is reacted with a 10% excess of the alkyne at a temperature between 45 and 60 °C in an ethereal solvent. On the other hand, the non-stabilised and highly electrophilic diphenylcarbene pentacarbonylchromium complex needs to be stored and handled at temperatures below -20 °C, which allows one to carry out benzannulation reactions at room temperature [34]. Recently, the first syntheses of tricyclic carbene complexes derived from diazo precursors have been performed and applied to benzannulation [35a,b]. The reaction of the non-planar dibenzocycloheptenylidene complex 28 with 1-hexyne afforded the Cr(CO)3-coordinated tetracyclic benzannulation product 29 in a completely regio- and diastereoselective way [35c] (Scheme 18). 

An interesting one-pot hydroformylation/Fischer indole sequence can be achieved by running the hydroformylation in the presence of a phenylhy-drazine. This protocol gave access to the methyl ester of the plant growth regulator 3-indole butanoic acid (IBA) (Scheme 16) [61-63]. A review on related tandem processes involving the hydroformylation as a key step has appeared recently [9]. 

Only the volumetric Karl Fischer titration (see Basic Protocol) will be discussed in this unit. In addition, it is assumed that the sample being tested is a low-moisture solid, where it is necessary to weigh out the sample, add it to a sealable flask of anhydrous methanol to extract the water, and measure the amount of extracted water. 

Most titrators have a sealed titration vessel where liquid samples are injected and the titrator adds the Karl Fischer reagent until a stable endpoint is achieved. This protocol... 

Though the protocol was written for a dry solid, it should also be mentioned that liquid samples can also be run (Firestone, 1998). Liquid samples can be added directly to the vessel itself or can be treated as a solid with an extraction step in the Karl Fischer solvent as presented in the protocol. The preference for moisture analyses is the gravimetric method (unit aj.i) largely due the higher costs of equipment and the use of chemicals in the Karl Fischer method. Currently one observes very few applications of the Karl Fischer method on food products published by the AOAC for nutritional labeling purposes. In particular, these food products are cocoa, cocoa products, confectionery coatings, and molasses (Sullivan and Carpenter, 1993). 

Enache et al. (2002) Ti, Zr oxide supported Co Support effects on phase formation, activation protocol optimization + + n.a. Preparation of Fischer Tropsch catalyst... 

Purine (6) itself is a colorless crystalline weak base which was first prepared by Fischer " the first synthesis using the Traubc condensation was reported by Isay. The Traube protocol is probably the best method to prepare purine, using pyrimidine-4,5-diamine as precursor and formic acid in an atmosphere of carbon dioxide or diethoxymethyl acetate as cyclizing reagents. 

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