Similarity reagents

Fonnation of C-X bonds is not normally a problem but the Grignaid route can occasionally be useful when normal halogen exchange fuls. Thus iodination of Me3(XH2CI cannot be achieved by reaction with Nal or similar reagents but direct iodinadon of the conesponding Grignaid effects a smooth conversion ... 

More recent examples have employed a milder reagent system, triphenyl-phosphine and dibromotetrachloroethane to generate a bromo-oxazoline, which is subsequently dehydrohalogenated. Wipf and Lim utilized their method to transform intermediate 11 into the 2,4-disubstituted system of (+)-Hennoxazole k Subsequently, Morwick and coworkers reported a generalized approach to 2,4-disubstituted oxazoles from amino acids using a similar reagent combination, triphenylphosphine and hexachloroethane. ... 

Sometimes lateral chlorination can occur on a methyl or alkylthio substituent, especially when phosphorus pentachloride or its mixtures with phosphoryl chloride are used (91JHC1549). Reactions of 2-methyl-4(I//)-quinoline (67) exemplify this behavior (81CPB1069) (Scheme 31) 2-chloro-3- and -4-methyquinolines are also subject to methyl chlorinations by similar reagents (91JHC1549). Sulfuryl chloride and NCS are also likely to induce a proportion of lateral chlorination (83KFZ1055 86S835). 

The Gabriel-Cromwell aziridine synthesis involves nucleophilic addition of a formal nitrene equivalent to a 2-haloacrylate or similar reagent [29]. Thus, there is an initial Michael addition, followed by protonation and 3-exo-tet ring-closure. Asymmetric variants of the reaction have been reported. N-(2-Bromo)acryloyl camphor-sultam, for example, reacts with a range of amines to give N-substituted (azir-idinyl)acylsultams (Scheme 4.23) [30]. 

Also, desymmetrization of prochiral hydroxyalkylphosphine P-boranes was successfully performed using similar reagents and conditions. In the case of bis(hydroxymethyl)phenylphosphine P-borane 87, both its acetylation and hydrolysis of the diacetyl derivative 89 gave good results, although in addition to the expected monoacetate 88, the diol 87 and diacetate 89 were always present in the reaction mixture (Equation 42). °°... 

With proof-of-concept on the direct methylation in hand, the optimization of the methylation with respect to regioselectivity, yield and isolation conditions was initiated to eliminate the use of 1,4-dioxane and LiH (Table 6.3). Under similar reagent/base conditions (Me2S04, LiOt-Bu), better selectivity was observed in nonpolar solvents (entries 2 and 3) than in polar (entry 1) and aprotic solvents (entries 4 and 5). Mel was a better methylation reagent than dimethyl sulfate under otherwise the same reaction conditions (entries 5 and 7). 

Most operations treating PGM sulphide-dominated ores have similar reagent schemes, with maybe a different choice of hydrophobic gangue depressants. Most of these plants use CuSC>4 as the principal sulphide activator. 

Similar reagents, although more limited, are RsSiOTeF and Hg(OSeF5)2. 

While the parent carboranes can be made from formaldehyde and decaborane, carboranes with substituents at the cage carbon can easily be synthesized from the appropriate aldehyde. For example, benzaldehyde and B10H14 give the zW(9-6-Ph-6-CB9Hn anion in 94% yield.92 The phenyl carborane formed is nido- not arachno- but subsequent carborane products can be made using similar reagents as for the parent arachno-6-CB9H14-.93... 

Cyanohydrin diethyl phosphates 87, easily accessible from propargyl aldehydes or ketones of type 86, reacted with lithium dialkylcuprates or similar reagents via an Sn2 process to give cyanoallenes in moderate to good yields [135]. The transformations 80 —> 81 and 84 —> 85 are only formally also SN2 reactions. Thus, plausible catalytic cycles, which include different short-lived palladium intermediates, have been postulated to explain these nucleophilic substitution reactions [127, 134],... 

A very similar reagent is benzyl t-butyl imidodicarboxy late 27, which is prepared from benzyl alcohol and benzoyl isocyanate, followed by exhaustive acylation with t-butoxycarbonyl chloride. Aminolysis of the resulting triacylamine yields 27. Treatment of the sodium salt of compound 27 with alkyl halides, followed by hydrolysis, gives primary amines53. 

The most widely used support substance for the manufacture of packing materials in analytical HPLC columns is silica. Silica can be treated with organochlorosilanes or similar reagents to produce siloxane linkages of any derived polarity similar to what is done for GC columns (stationary phases). The most popular materials are octadecyl silane (ODS), which contains a carbon loading of CIS groups and octyl, which contains C8 groups materials such C2, C6, and C22 are also available. 

Affinity Labeling of Catalytic ATP Sites. Residues involved in ATP binding are potentially revealed by the use of affinity labels that are based on ATP s structure. Perhaps the most systematically studied of these compounds is 5 -fluorosulfonylbenzoyladenosine (5 -FSBA) (Figure 3a), which has been reported to label at least six kinases (32-A1). In the case of rabbit muscle pyruvate kinase such work has Indicated the presence of a tyrosine residue within the metal nucleotide binding site and an essential cysteine residue located at or near the free metal binding site (32). A similar reagent, 5 -FSBGuanosine, revealed the presence of two cysteine residues at the catalytic site of this same enzyme, both distinct residues from those modified by 5 -FSBA (33,34). With yeast pyruvate kinase both tyrosine and cysteine residues were modified by 5 -FSBA at the catalytic site ( ), and with porcine cAMP-dependent protein kinase a lysine residue was labeled at the active site (36). 

Fluorinations with similar reagents (VF5, SbF5, and AsF3) are described in this volume (see Sections 11. and 12.)... 

Ligand. Used for Pd-catalyzed reactions of aryl and vinyl halides and triflates. Also for Kumuda coupling reactions. See Dppe for a similar reagent. 

Cyclopropanation reagent. A similar reagent, prepared from EtZnI + CH2I2, [I-CH2-Zn-Et] [33598-72-0] is known as the Sawada Reagent. [P. Knochel, Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995,4 2473]... 

Notes For a similar reagent, see DAD (Dimethylaluminum 2,6-Di-r-butyl-4-methylphenoxide) [86803-85-2]... 

In these complexes, the gold-metal bonds are apparently weak and polar and, in man cases, the metal carbonyl anion can be displaced by donor ligands (equation go)716 726>732,733 a well as by halogens and similar reagents.721... 

Hydrido complexes can be prepared by the oxidative addition of hydrogen to coordinatively unsaturated metals (e.g. Vaska s compound) or by reduction of higher valent compounds with borohydride or similar reagents. 

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