The Reactions of PH

To my knowledge, the first transition metal-catalyzed reaction utilizing S-S bond activation was reported by Holmquist el al. in 1960 [14]. The reaction of (PhS)2 with CO (950 atm) in the presence of chromium oxide on AI2O3 at 275°C furnished thioester 57 in 31% yield (Eq. 7.42). 

A similar nitrene intermediate can also be postulated in the mechanism of nitrosobenzene hydrogenation. Indeed a standard way of producing Ph-N is from the reaction of Ph-NO with PPhs (17). In the hydrogenation of nitrosobenzene the principal product in the early stages is azoxybenzene [7, 18]. It was suggested that azoxybenzene was formed by the following sequence ... 

The reaction of Ph 3P=CH2 with benzoyl isocyanate takes place in a 1 2 ratio with loss of benzene to afford the ylide 173 <71JOC2029> and treatment of either Ph3P=CHC02Me or Ph3P=CHC02Et with aryl cyanates, Ar-O-CN, results in formation of the pyrimidine ylides 174 <67CB187>. An alternative means of access to 171 (R = cyclohexyl) is provided by... 

The introduction of the novel educt l,2,3,4-tetraphenyl-l,2,3,4-tetra-p-tolylcyclotetra-silane enables the selective monofunctionalization of perarylated cyclotetrasilanes54. [Ph(p-Tol)Si4] is easily prepared by the reaction of [Ph(p-Tol)SiCl2 with lithium and shows significantly higher solubility and reactivity compared to (S iPli2)4- From [Ph(p-Tol)Si4] the monofunctional cyclotetrasilane derivatives Si4Ph4(/ -Tol)3X with X = OSO2CF3, F, Cl, Br, I, H or t-Bu are accessible simply by dearylation with triflic acid and... 

Trifluoroacetoxygermane 162 obtained by the reaction of Ph Ge with CF3COOH is a rare example of a pentacoordinated germanium compound where intramolecular coordination leads to formation of four-membered chelate ring517,518. In solution, aO Ge coordination in 162 was deduced on the basis of the IR spectrum. The v(C=0) absorption band (1745 cm-1) is about 80 cm-1 lower than that in CF3COOH. According to X-ray... 

The reaction of PhS" ion with 4-bromobenzophenone (154a) and 4-haloacetophenones (154b) was studied in MeCN, DMSO and DMF under thermal (A, 60 °C) or photochemical activation to yield 80-97% yield of products 208 (equation 146)271. 

Compounds of type XXV have been obtained by the reaction of Ph As(0Me)5- (n = 2 or 3) with a diol. It has been observed that compounds containing two rings are thermodynamically more stable than compounds with one ring. This is independent of ring size. 

The relative rates of the reaction of PhS with tricyclo[4.1.0.0 ]heptanes were found to depend on the substituents at the bridgehead position. A linear correlation was observed between the relative rates and the vertical ionization potentials of the substrate... 

A series of alkenyl complexes (214, 216, and 218) were prepared from the reaction of PhS with the alkyne complex 213, the / -allene complex 215, and the cationic complex 217. Complex 218, with the nucleophile linked at the a position, could be converted to an allenacyl complex (219) by the addition of CO and a catalytic amount of oxidant, such as [Cp2Fe][Bp4] or Ce VEtOH. Excess Ce VEtOH leads to the formation of an alkenyl ester, (EtO)C(0)C(Me)=C(Me)SPh (153). 

The parent material for this particular hydrogenation, PtRu5(CO)jj(p-SnPhj) (Pg-C), was obtained from the reaction of Ph SnH with the hexanuclear cluster complex PtRUj(CO)jg(pg-C) - see Fig. 21.5b. The heterotrinuclear (Ru-Pt-Sn) complex was anchored to a mesoporous silica (38 A diameter) via the silanol groups, as previously described [49, 50]. 

The reaction of Ph(CH2)2PCl2 with zinc chloride at 170°, followed by hydrolysis with hot hydrochloric acid and oxidation with bromine affords 1-hydroxy-1,2,3,4-tetrahydro-phosphinoline 1-oxide (17) in very good yield, incomplete oxidation yields 1,2,3,4-tetrahydrophosphinoline 1-oxide. 

The reaction of Ph Sn with PhMgBr, in contrast to Eq. (a), leads to a compound that behaves like an adduct of Ph2Sn with PhMgBr. 

Variations in monofunctional adduct lifetimes were also invoked to explain the relative ratios of different platinum adducts formed by cis-DDP on DNA. When the reaction of PH][Pt(en)Cl2] with DNA was allowed to occur in the presence of thiourea, subsequent enzymatic digestion of the... 

The results of early ICR investigations of the reactions of PH with PH3, NH3, HjO, and CH4 [42] agree with the more recent ICR investigation only in the case of CH4, but reactions of the other molecules gave fewer products and lower rate constants [43]. In the reaction of PH3 with HjO upon exposure to an electron beam, the intermediately formed PH was identified to be the precursor of HPO and HjPO. Ions containing more oxygen atoms did not form [42] the formation of the species H ,PO with m 0 to 3 and n = 2 to 4 [44] could not be confirmed [42]. 

To test the validity of this mechanism, it was reasoned that a weak add (t-BuOH or water) should quench the zwitterion 21 and suppress or at least decrease the formation of by-products. This is indeed the case, although the addition of more alkene increases the quantity of by-products, even in the presence of t-BuOH. It should be noted that the presence of these protic additives is not innocent, since it also increases the reaction rates and affects the enantioselectivity. For example adding 20 equivalents of t-BuOH to the reaction of PH(Is)Me with tert-butyl acrylate halves the time for the completion of the reaction (from 5 to 2 days) and doubles the enantiomeric excess from 28% to 56%. The latter enantioselectivity is the best obtained to date with the systems discussed in this section. More evidence for the Michael addition mechanism came from trapping intermediate 21 with electrophiles other than a proton. Scheme 6.12 shows that performing the hydrophosphination reaction in the presence of benzaldehyde produced some of the three-component coupling product 25. 

Another factor to be considered is the stability of the radical anion intermediate of the substimtion product (ArNu ). For example, the reaction of Ph" radical with CH CN anion affords the radical anion 8 that by intramolecular ET fragments into PhCH radical and CN ions (Scheme 10.7), PhMe being the principal product observed by H abstraction from the solvent (S-H) [19]. 

The ion-molecule reactions that occur in mixtures of SiH4 and PH3 have recently been described As in the aforementioned cases, the main reaction channels for the formation of larger-sized clusters from SiH " cations (n = 0-3) and PH3, and from the reactions of PH t+ cations (n = 0-3) with SiH4, correspond to the addition of the neutral molecule and dissipation of the excess energy via loss of a hydrogen molecule. It was concluded in this study that the nucleation of mixed silicon-phosphorous ions was favored upon ionization of mixtures that contain a large excess of SiH4. 

Cross-coupling Reactions. Triphenyl(difluoro)silicates arise from the reaction of Phs SiH and quaternary onium hydrogendiflu-oride. These species can then be subject to cross-coupling phenyla-tion reactions under Pd-catalysis. Usefully, no homocoupled product formation was observed under these conditions (eq 32). ... 

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