Dppp

Triflates of phenols are carbonylated to form aromatic esters by using PhjP[328]. The reaction is 500 times faster if dppp is used[329]. This reaction is a good preparative method for benzoates from phenols and naphthoates (473) from naphthols. Carbonylation of the bis-triflate of axially chiral 1,1 -binaphthyl-2,2 -diol (474) using dppp was claimed to give the monocarboxy-late 475(330]. However, the optically pure dicarboxylate 476 is obtained under similar conditions[331]. The use of 4.4 equiv. of a hindered amine (ethyldiisopropylamine) is crucial for the dicarbonylation. The use of more or less than 4.4 equiv. of the amine gives the monoester 475. 

Carbonylation of enol triflates derived from ketones and aldehydes affords Q,/)-unsaturated esters[332]. Steroidal esters are produced via their aryl and enol triflates[328]. The enol triflate in 477 is more reactive than the aryl tritlate and the carbonylation proceeds stepwise. First, carbonylation of the enol triflate affords the amide 478 and then the ester 479 is obtained in DMSO using dppp[333]. 

For coupling, the cheaper aryl fluorosulfonate 713 is used as an alternative to the expensive aryl triflates to give the same results[473]. The arenesulfonates 714 are active for the reaction with vinylstannanes when dppp and LiCI are used in DMSO[583], The bromide 715 attacks the arylstannane moiety selectively without reacting with the organoboron moiety in 716 in the absence of a base[584]. 

Phosphine oxides are prepared similarly[644]. Selective monophosphiny-lation of 2,2 -bis[(lrifluoromethanesulfonyl)oxy]-l,1 -binaphthyl (784) with diphenylphosphine oxide using dppb or dppp as a ligand takes place to give optically active 2-(diarylphosphino)-1,1 -binaphthyl (785). No bis-substitution is observed[645,646]. 

The enone 807 is converted into the dienol triflatc 808 and then the conjugated diene 809 by the hydrogenolysis with tributylammonium for-mate[689,690]. Naphthol can be converted into naphthalene by the hydrogenolysis of its triflate 810[691-693] or sulfonates using dppp or dppf as a ligand[694]. Aryl tetrazoyl ether 811 is cleaved with formic acid using Pd on carbon as a catalyst[695]. 

Allylamines are not easily cleaved with Pd catalysts, but the carbonylation of the allylic amine 395 proceeds at 110 C to give the /3,7-unsaturated amide 396 by using dppp as a ligand[252], Dccarboxylation-carbonylation of allyl diethyl-carbamate under severe conditions (100 C, 80 atm) affords /3,7-unsaturated amides[2531. The 3-vinylaziridine 397 is converted into the a-vinyl-J-lactam 398 under mild conditions[254]. 

When a bidentate phosphine is used as a ligand for the reaction of J-keto esters or /i-diketones, no dimerization takes place. Only a 2-butenyl group is introduced to give 68[49,62], Substituted dienes such as isoprene, 1,3-cyclohexa-diene, and ocimene react with carbon nucleophiles to give a mixture of possible regio- and stereoisomers of 1 1 adducts when dppp is used as a ligand[63,64]. 

The allenyl moiety (2,3-aikadienyl system) in the carbonylation products is a reactive system and further reactions such as intramolecular Diels-Alder and ene reactions are possible by introducing another double bond at suitable positions of the starting 2-alkynyl carbonates. For example, the propargylic carbonate 33 which has l,8(or 1.9)-diene-3-yne system undergoes tandem carbonylation and intramolecular Diels-Alder reaction to afford the polycyclic compound 34 under mild conditions (60 C, 1 atm). The use of dppp as ligand is important. One of the double bonds of the allenyl ester behaves as part of the dieneflSj. 

Ethyl /m s -2-butenyl sulfone (86) together with some ethyl vinyl sulfone are obtained by the reaction of ethylene and. SO2 in wet benzene using PdCl2. SO2 behaves mechanistically similarly to CO in this reaction[66]. Hydrosulfination of alkenes with SO2 and H2 is catalyzed by the Pd(dppp) complex. The sulfinic acid 87 is a primary product, which reacts further to give the. S-alkyl alkanethiosulfonates 88 as the major product, and 89 and the sulfonic acid 90 as minor products[67]. 

DIBAL, NiCl2(dppp), toluene, CH2CI2, THF, or ether, 80-97% yield. These conditions are chemoselective for simple alkyl and phenolic allyl ethers. More highly substituted allyl ethers are unreactive. 

Returning briefly to CO2 as a ligand in addition to the various mono-C02 complexes referred to above, several bis(rj -CO2) transition-metal adducts are known, e.g. /ran -[Mo( ) -C02)2(PMe3)4] (5) and trans.mer-[Mo( 2-C02)2(PMc3)3(CNPr )].< 22 The first homo-bimetallic bridging-C02 complex has also been structurally characterized by X-ray analysis, viz. [(dppp)(CO)2Re(/x, j 0,0 j C)Re(CO)3(dppp)] (6) [dppp = l,3-bis(diphenyl-phosphino)propanc]. 0 3)... 

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

Abbreviations aapy, 2-acetamidopyridine Aik, alkyl AN, acetoniuile Ar, aryl Bu, butyl cod, 1,5-cyclooctadiene COE, cyclooctene COT, cyclooctatetraene Cp, cyclopentadienyl Cp , penta-methylcyclopentadienyl Cy, cyclohexyl DME, 1,2-dimethoxyethane DME, dimethylformamide DMSO, dimethyl sulfoxide dmpe, dimethylphosphinoethane dppe, diphenylphosphinoethane dppm, diphenylphosphinomethane dppp, diphenylphosphinopropane Et, ethyl Ec, feirocenyl ind, inda-zolyl Me, methyl Mes, mesitylene nb, norbomene orbicyclo[2.2.1]heptene nbd, 2,5-norbomadiene OTf, uiflate Ph, phenyl PPN, bis(triphenylphosphoranylidene)ammonium Pi , propyl py, pyridine pz, pyrazolate pz, substituted pyi azolate pz , 3,5-dimethylpyrazolate quin, quinolin-8-olate solv, solvent tfb, teti afluorobenzobaiTelene THE, tetrahydrofuran THT, tetrahydrothiophene tmeda, teti amethylethylenediamine Tol, tolyl Tp, HB(C3H3N2)3 Tp , HB(3,5-Me2C3HN2)3 Tp, substituted hydrotiis(pyrazol-l-yl)borate Ts, tosyl tz, 1,2,4-triazolate Vin, vinyl. 

The regioselective arylation of butyl vinyl ether was carried out by the same group, using Pd(OAc)2 as catalyst precursor and l,3-bis(diphenylphosphino)-propane (dppp) as the ligand, dissolved in [BMIM][Bp4] (Scheme 5.2-17) [90]. 

Scheme 1-27. Synthesis of alkoxy PTV derivatives and dibutoxy PTV 79 a) BuLi, MgBr2-Et20 b) CICH=CHCI (0.5 equiv.), NiCl2(dppp)2 c) ClCH=CHCl (1 equiv.), NiCI2(dppp)2.

PtCl2(cod) dppp > PtCl2(dppp) dppp > Pd(dppp)2... 

Hydrogen reduction of (dppp)Pd(CF3S03)2(dppp)Ph2P(CH2)3PPh2 affords [dpppPd]2(CF3S03)2, which has agonistic Pd-phenyl interactions as well as normal Pd-P coordination and a Pd-Pd bond (2.701 A) (Figure 3.21). 

Figure 3.21 Structure of the dimeric palladium(I) complex [(dppp)Pd]2(CF3 S03)2. (Reprinted with permission from Organometallics, 1992, 11, 23. Copyright (1992) American Chemical Society.)...

Other examples that involve intermediate allyl cations are illustrated in Scheme 1.4. The cationic palladium(II) complex [Pd(dppp)(PhCN)2](BF4)2 coordinates the carbonyl oxygen of benzaldehyde and the activated carbonyl carbon attacks the isoprene, forming the allyl cation 10 which then cyclizes to give the 4-methyl-6-phenyl-5,6-dihydro-2H-pyran [22]. 2-Oxopropyl acrylate 11, in the presence of trimethylsilyltrifluoromethane sulfonate (TMSOTf) and methoxytrimethylsilane (MeOSMT), generates the cation 11a which is an efficient dienophile that reacts easily with the cyclohexadiene to give the Diels-Alder adduct in good yield [23]. 

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