Dehalogenation reaction between

Figure 5. The initial step of nucleophilic dehalogenation reaction between alachlor and thiosulfate salts (A) and fumigants and thiosulfate salts (B)...

Hydroxyphthalazin-l(2//)-one is obtained in a smooth reaction between phthalic anhydride and hydrazine hydrate and this is again the starting compound for many 1-substituted and/or 1,4-disubstituted phthalazines. The transformations of 1,4-dichloro-phthalazine, which is prepared in the usual manner, follow a similar pattern as shown for pyridazines in Scheme 110. On the other hand, phthalonitrile is the preferential starting compound for amino- and hydrazino-phthalazines. The most satisfactory synthesis of phthalazine is the reaction between a,a,a, a -tetrachloro-o-xylene and hydrazine sulfate in sulfuric acid (67FRP1438827), alt iough catalytic dehalogenation of 1-chloro- or 1,4-dichloro-phthalazine or oxidation of 1-hydrazinophthalazine also provides the parent compound in moderate yield. 

The C-C coupling reaction between RMgX and R X is considered to proceed though an Ni(R)(R )Lm intermediate, and acceleration of the reductive elimination of R-R by coordination with olefinic or aromatic R X to Ni(R)(R )Lm is necessitated for a smooth catalytic reaction [15,16]. On these bases Ni-pro-moted dehalogenative polycondensation of dihalo organic compounds is suited to the preparation of 7i-conjugated aromatic and olefinic polymers. 

Oxidative addition of C2 - H bonds of imidazolium salts to low valent metals was first observed by Nolan and coworkers in 2001, who proposed a NHC - Pd - H intermediate in the catalytic cycle of the dehalogenation of aryl halides with Pd(dba)2 in the presence of imidazolium salts [154]. More direct evidence of this process was described by Crabtree and coworkers two years later [155]. The reaction between a pyridine-imidazolium salt and Pd2(dba)3 afforded the preparation of bis-NHC - Pd(II) complexes by C2 - H oxidative addition (Scheme 40). The presumed Pd - H intermediates were not detected. The authors proposed a mechanism via two successive C - H oxidative additions followed by reductive elimination of H2 [ 155]. 

Those Michaelis-Becker reactions between even relatively simple primary or benzylic-type halides and sodium dialkyl phosphites are not without their unwanted side-reactions. Halomethylfurylcarboxylic esters, for example, undergo concomitant dehalogenation or Michaelis-Becker phosphonation (the two processes may also occur side by side) depending on the relative positions in the furan nucleus of both carboxylic ester and halomethyl groups and on the halogen. Chlorides react normally, bromides do not . 

Cuprous chloride tends to form water-soluble complexes with lower olefins and acts as an IPTC catalyst, e.g., in the two-phase hydrolysis of alkyl chlorides to alcohols with sodium carboxylate solution [10,151] and in the Prins reactions between 1-alkenes and aqueous formaldehyde in the presence of HCl to form 1,3-glycols [10]. Similarly, water-soluble rhodium-based catalysts (4-diphenylphosphinobenzoic acid and tri-Cs-io-alkylmethylam-monium chlorides) were used as IPTC catalysts for the hydroformylation of hexene, dodecene, and hexadecene to produce aldehydes for the fine chemicals market [152]. Palladium diphenyl(potassium sulfonatobenzyl)phosphine and its oxide complexes catalyzed the IPTC dehalogenation reactions of allyl and benzyl halides [153]. Allylic substrates such as cinnamyl ethyl carbonate and nucleophiles such as ethyl acetoactate and acetyl acetone catalyzed by a water-soluble bis(dibenzylideneacetone)palladium or palladium complex of sulfonated triphenylphosphine gave regio- and stereo-specific alkylation products in quantitative yields [154]. Ito et al. used a self-assembled nanocage as an IPTC catalyst for the Wacker oxidation of styrene catalyzed by (en)Pd(N03) [155]. 

Hydrostannolysis is usually a reaction in which the bond between alkyl (or aryl) group and halogen or sulfur is cleaved reductively by an organotin hydride. In particular, hydrostannolysis is available for the dehalogenation reaction of a halide as shown in eq. (10.12). This reduction usually occurs in a stepwise fashion, the... 

Since the reaction between HOCs and thiosulfate followed second-order kinetics, and that and dehalogenated HOC-thiosulfate derivative was formed as one of the initial products, it may be concluded that the reaction followed a pathway as depicted for alachlor in Figure SA or for fumigants in general in Figure 5B. 

Dialkyl phosphonate (1) is known to be present in tautomerism with dialkyl phosphite (2). Although the phosphonate form mainly exists under neutral conditions, the equilibrium to phosphite is observed under basic conditions. The interconversion between P(V) and P(III) species shown in Scheme 2.1 is considered to contribute to the redox processes, hi this section, the dehalogenation reaction depending on the tautomerism is described. 

The model reaction between bromo benzene and phenylacetylene gives information about the chain limiting reactions and defect structures in the polymer (76). The dehalogenation can be neglected in contrast to die Heck reaction. Diin and enin formation as well as trimerization are demonstrated in the model reaction. The trimerization and the formation of enin can be suppressed quantitatively. The formation of diin occurs in die range < 0,5 %. It is not clear if the diin is formed during the reaction or on working up. 

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