Triphenylphosphine, substitute found

Crystallography of two cationic complexes which result from substitution of chloride in (30) with triphenylphosphine were found to have dissimilar structures. The structure of the hexa-fluorophosphinate is similar to the neutral complexes (C—S bond = 177 pm) while the perchlorate is unusual (C—S bond =168 pm). This shortening of the C—S bond in the perchlorate is accompanied by a lengthening of the M—C bond (15 pm) and is probably due to the influence of the perchlorate ion on crystal packing. The M—S bonds of both types of sulfur compounds are significantly longer than the M—C bonds (9-33 pm) which is consistent with sulfur s longer covalent radius. 

The Suzuki reaction has been successfully used to introduce new C - C bonds into 2-pyridones [75,83,84]. The use of microwave irradiation in transition-metal-catalyzed transformations is reported to decrease reaction times [52]. Still, there is, to our knowledge, only one example where a microwave-assisted Suzuki reaction has been performed on a quinolin-2(lH)-one or any other 2-pyridone containing heterocycle. Glasnov et al. described a Suzuki reaction of 4-chloro-quinolin-2(lff)-one with phenylboronic acid in presence of a palladium-catalyst under microwave irradiation (Scheme 13) [53]. After screening different conditions to improve the conversion and isolated yield of the desired aryl substituted quinolin-2( lff)-one 47, they found that a combination of palladium acetate and triphenylphosphine as catalyst (0.5 mol %), a 3 1 mixture of 1,2-dimethoxyethane (DME) and water as solvent, triethyl-amine as base, and irradiation for 30 min at 150 °C gave the best result. Crucial for the reaction was the temperature and the amount of water in the... 

Unfortunately, several less direct observations indicate that the kinetic conclusions found in the substitution of Ir4(C0)i2 are not easily generalized. For instance, it is known that progressive substitution in other clusters, such as Ru3(CO)jo(NO)2205 and Co3(CO)9CR44 always exhibit predominantly SN1 kinetics. Moreover, it is also known that there is no large increase in the relative rates of substitution in either Co4(CO)j2 48> or Rh4(CO)i2 61 25° since both these clusters react with a stoichiometric amount of triphenylphosphine to give essentially the monosubstituted cluster. 

Previous work has shown that the electronic characteristics of the benzene substituent in triarylphosphine chlororhodium complexes have a marked influence on the rate of olefin hydrogenation catalyzed by these compounds. Thus, in the hydrogenation of cyclohexene using L3RhCl the rate decreased as L = tri-p-methoxyphenylphosphine > triphenylphosphine > tri-p-fluorophenylphosphine (14). In the hydrogenation of 1-hexene with catalysts prepared by treating dicyclooctene rhodium chloride with 2.2-2.5 equivalents of substituted triarylphosphines, the substituent effect on the rate was p-methoxy > p-methyl >> p-chloro (15). No mention could be found of any product stereochemistry studies using this type of catalyst. 

Barton and coworkers exploited this strategy in the preparation of overcrowded ethylenes456 usually the desulfurization of a thiirane is accomplished by one equivalent of tertiary phosphine, mainly triphenylphosphine. However, spontaneous loss of sulfur from thiiranes substituted by aryl or halogen has sporadically been reported. Huisgen has reviewed this subject455 and performed many kinetic studies. He found that the desulfurization step can be accomplished by catalytic thiolates and also by thiobenzophenone or other thioketones, although in this case the reaction is slower (equation 131). 

One of the most used resins in solid-phase combinatorial organic synthesis, which has found a myriad of applications, is the Merrifield resin (17).61 This resin is also the building block for a tremendous amount of novel resins being developed in combinatorial chemistry with applications in both solid-phase as well as solid-phase-assisted solution-phase combinatorial chemistry. A recent, useful, and novel example is the report of its being employed as a triphenylphosphine scavenging resin.76 During the conversion of azidomethylbenzene (51) into benzylamine, excess triphenyl-phosphine is allowed to react with Merrifield resin (17) in the presence of sodium iodide in acetone. A phosphonium-substituted resin (52) is thus formed. Upon simple filtration, pure benzylamine is isolated as shown in Fig. 22. 

Lhommet and his group [182] have tackled the difficult creation of tetra-substituted C-C double bonds through the Eschenmoser reaction. They found conditions to overcome the unfavourable alkylation with secondary a-bromo esters slow addition of triethylamine and triphenylphosphine to a solution of thiolactam and a-bromo ester. In this way the thioiminium salt was trapped as soon as it was formed. 

Reaction of the aldehyde (86) with methyl azidoacetate in the presence of sodium methoxide was found to proceed smoothly to give azide (255), which upon thermolysis in boiling toluene gave dimethyl l-methyl-7//-furo[3,2-6 4,5-6 ]dipyrrole-2,6-dicarboxylate (256). Compound (255) reacted with triphenylphosphine in dry dichloromethane to give the iminophosphorane (257), which with phenyl or 3-chlorophenyl isocyanate in dry toluene under reflux gave the substituted pyrrolo-[2,3 4,5]furo[3,2-c]pyridines (258) or (259) via carbodiimides, which were not isolated (Scheme 16). The compounds (8i), (84), and (87) undergo similar reactions <92M807,94H(37)1695>. 

Among the more unusual modes of epoxide reactivity is a technique for reductive deoxygenation using a system of triphenylphosphine and iodine in dimethylformamide (DMF). Under these conditions, the functionalized epoxide 98 was quantitatively converted to the diallyl ether 99. Similar conditions were found to convert epoxides to the interestingly substituted (5-bromoformate derivatives (e.g. 101) <02T7037>. 

Substitution of CO in (fl-C3H5)Fe(CO)3l also involves an associative process 149), while Heck 150) has found that CO replacement by triphenylphosphine in five-coordinate (7t-C3H5)Co(CO)3 is a D-type reaction in spite of the coordinative unsaturation of the metal in the starting complex. 

Catalysts which have been found to promote dimerization of phenyl isocyanate include pyridine (11), methylpyridine (12), triethylamine (13), X-methyl- (or ethyl-)morpholine, triethylphosphine, and other alkyl or alkyl-arylphosphines (14, 15). Alkylphosphines bring about a very violent polymerization since they act as active catalysts and the polymerization is quite exothermic. Triphenylphosphine is inactive. Alkyl-arylphosphines are not as active as alkylphosphines and permit better control of the reaction. Another convenient method (14, 16) for control of phosphine-catalyzed dimerization involves the addition of an alkylating agent such as benzyl chloride in an amount stoichioraetrically equivalent to the substituted phosphine present. Complete deactivation of the catalyst results. By this means the reaction may be mitigated or even quenched and then activated by the addition of more catalyst. 

Metallated spirobicyclicphosphoranes 96a-c were found to undergo carbonyl substitution reactions with triphenylphosphine in toluene to form (97a-c) and the isolated products were characterised by IR, H nmr, elemental analysis and thermo-gravimeteric studies. There was no evidence for insertion of CO into the pentaco-ordinate P -Mn bond. 

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