Schwarz reagent

The presence of electron-withdrawing substituents is not always an indispensable condition to make the insertion quantitative. Schwarz has indeed established an important application of alkene insertion in the Zr-H bond of the so-called Schwarz reagent, [ZrCp2(H)(Cl)]. 

The regiospecificity of the above reaction is antiMarkownikov, which yields a primary alkyl complex. In addition, if the Schwarz reagent reacts with 2-butene, the insertion product is an instable secondary alkyl complex, this kinetic instability being presumably due to the steric bulk. This latter complex rearranges to give a primary alkyl complex by p-H elimination followed by regiospecific insertion of the intermediate 1-butene. 

What is the reaction product between Schwarz reagent [ZrCp2(Cl)(H)] and cyclopentadiene ... 

The chemistry of zirconocene derivatives mostly attracted attention on two aspects. First, Schwarz reagent [ZrCp2(H)(Cl)] is able to regiospecifically insert olefins into the Zr-Fl bond (see Chaps 6 and 21). Then, a second more recent aspect is the zirconocene-based initiation of olefin polymerization with 14-electron precursor complexes of the type [ZrCp2(Me)]+ (see Chap. 15.1). 

Iwata et al. also established the direct catalytic asymmetric aldol reaction of thioamides (Scheme 8.39)." Treatment of an aldehyde and thioamide 259 in the presence of the catalyst containing [Cu(MeCN)4]BF4, (7 ,/ )-Ph-BPE, and lithium phenoxide 260 gave (3-hydroxythioamide 261 in good yield with high stereoselectivity. Thioamide features the direct transformation into aldehyde by using a Schwarz reagent (Scheme 8.40)." They converted aldol adduct 261 into (3-siloxyal-dehyde 262, which was further submitted to the direct stereoselective aldol reaction. Both diastereomers 263 and 264 were obtained in good yield. This protocol is effective to synthesize sequential 1,3-polyols. 

Since the purpose of this report is to illustrate the usefulness of Z-gel as a reagent for the separation of antigens from antigen-antibody complexes, the methods used for the purification of CEA and AFP will not be described. Bovine insulin was purchased from Schwarz-Mann, and anti-bovine insulin serum was purchased from Miles Laboratories. Antisera to CEA and AFP were prepared in goats and rabbits, respectively. Standard solutions of nonradioactive CEA (125 ng/ml) and AFP (180 ng/ml) are prepared in 50 mM borate buffer (pH 8.4) containing 10% (v/v) group A human plasma for CEA or 0.25% human albumin for AFP and 0.01% thimerosal. The bovine insulin standard (100 /u.IU/ml) is prepared in 40 mM phosphate buffer, pH 7.4, containing 0.15 M NaCl, 0.5% bovine serum albumin (BSA), and 0.01% thimerosal (phosphate buffer 1). 

Among the direct labeling methods, reduction of the antibody by a thiol reagent, such as mercaptoethanol or dithiothreitol, results in high labeling yields (Reilly 1993 Schwarz et al. 1988 Thakur et al. 1991). Table 2.3.2 compiles Tc-labeled antibodies approved as radiopharmaceuticals in the United States and the European Union. 

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