Diphenylphosphino Group Research Articles

Regioselective upper-rim functionalizations of calix[4]arene by diphenylphosphino groups

The regioselective upper-rim functionalization of calix[4]arene have been performed to prepare all the multisubstituted diphenylphosphine derivatives. In addition, the X-ray structures of 5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetra-n-propoxycalix[4]arene and 5,11,17,23-tetrakis(diphenylphosphino)-25,26,27,28-tetra-i-propoxy-calix[4]arene have been determined. Regioselective functionalizations have been achieved using methods that involve appropriate choices of bases, alkyllithium-solvent systems, stoichiometry, and reaction times. A new and convenient method for selectively preparing derivitized calix[4]arenes at proximal positions in relative large scale quantity has been developed and involves a transesterification of the distal diester derivative into the proximal isomer.Key words: calix[4]arenes, phosphine, upper-rim, X-ray structure, transesterification.

Ortho-Lithiated benzyl diorganophosphines [ o-(R 2PCH 2)C 6H 4Li(Et 2O)], R=Ph, Me. Synthesis, structural characterization, and reactions

( o-Lithiobenzyl)dimethylphosphine, [ o-(Me 2PCH 2)C 6H 4Li(Et 2O)] 2 ( 7), is shown by crystal structure analysis to be dimeric, the two lithium atoms bridging the phenyl ortho-carbon atoms in a four-membered ring structure. A distorted tetrahedral coordination sphere at lithium is completed by coordination of one phosphino group and a molecule of diethylether (triclinic, space group P1̄, a=10.986(3), b=11.160(3), c=12.368(4) Å, α=86.04(2), β=89.51(2), γ=83.04(2)°, Z=2). [ o-(Me 2PCH 2)C 6H 4Li(Et 2O)] 2 ( 7) cleanly reacts in donor solvents like diethylether to the thermodynamically more stable (α-lithiobenzyl)dimethylphosphine [Me 2PCHLi(Et 2O)C 6H 5] 2 ( 9) with the same overall composition. Crystal structure analysis of the latter shows each lithium atom to be now bonded in an η 2 fashion to the C benzylC ipso bond of one anion, the diethylether molecule, and to the phosphino group of the second anion thereby resulting in a dimeric structure with a central six-membered ring (triclinic, space group P1̄, a=8.482(3), b=9.388(3), c=9.482(3) Å, α=95.42(2), β=91.36(2), γ=104.20(2)°, Z=1). ( o-Lithiobenzyl)diphenylphosphine undergoes the same reaction to the corresponding α-lithiobenzylphosphine upon addition of strong donors like N, N, N′, N′-tetramethylethylenediamine (tmeda). Upon addition of Cp 2TiCl 2, ( o-lithiobenzyl)diphenylphosphine reacts to form 1,2-bis[ o-(diphenylphosphino)phenyl]ethane, [ o-(Ph 2P)C 6H 4CH 2] 2 ( 10), the formation of which is thought to proceed by oxidation of the anion [ o-(Ph 2PCH 2)C 6H 4] − by Cp 2TiCl 2 to the radical which undergoes a 1,3 shift of the diphenylphosphino group from the sp 3 benzyl carbon atom to the sp 2 ortho-carbon atom of the phenyl ring to form the more stable benzyl radical. Dimerization of the latter ultimately leads to [ o-(Ph 2P)C 6H 4CH 2] 2 ( 10) whose molecular structure was determined in the solid state (monoclinic, space group P2 1/ n, a=12.217(2), b=8.382(1), c=15.004(2) Å, β=90.81(1)°, Z=2). The same reaction occurs upon oxidation of ( o-lithiobenzyl)diphenylphosphine with ferricinium tetrafluoroborate, [Cp 2Fe] +BF 4 −, thus corroborating the proposed reaction sequence with the transition metal species acting solely as oxidizing agents.

Regioselective upper-rim functionalizations of calix[4]arene by diphenylphosphino groups

Regioselective upper-rim functionalizations of calix[4]arene by diphenylphosphino groups

4-(Diphenylphosphino)-9,9-dimethylxanthen-5-yl]diphenylphosphine oxide toluene hemisolvate

In the title compound, C39H32O2P2·0.5C7H8, there are two distinct phosphorus centers. The P—C bond lengths around the diphenylphosphino group are around 0.04 Å larger than those in the phosphine oxide moiety. This corresponds to smaller C—P—C bond angles of 101.2 (15)° compared to 108.4 (9)° for the latter. The rigid dibenzopyran backbone is folded at an angle of 158.9 (1)°.

A Synthetic Route to a New Surface-Active Phosphine Ligand: 12-DPDP (12-Diphenylphosphinododecylphosphonate)

A water-soluble phosphonate-functionalized phosphine ligand Na 2[Ph 2P(CH 2) 12PO 3] ( 8), was prepared in eight steps from cyclododecanone. Phosphine 8 reacts with [Rh(COD)Cl] 2 in methanol to give the new complex Na 2[Rh(COD)(Ph 2P(CH 2) 12PO 3)Cl] ( 9). Complex 9 is inactive in the catalytic hydrogenation of 1-hexene and cyclohexene due to the decomposition of 9 to rhodium metal in the presence of hydrogen gas. Hydrogenation of decene using [Rh(COD) 2]BF 4 and 3 equiv. of 8 in an aqueous emulsion was achieved using 1 atm H 2. 31P NMR studies on 8 suggest a lack of well-defined aggregation in water, which has been ascribed to the steric bulk of the diphenylphosphino group.

Third Generation of the Cp‘−P Ligand: Highly Stereoselective Control of Central Chirality Arising at a Metal Center

A new type of Cp‘−P ligand (the third generation of the Cp‘−P ligand), [{3-(NM)Ind−P}n=2]H (3a), in which an indenyl group, having a neomenthyl group, and a diphenylphosphino group are connected by an ethylene group, was designed and prepared. The presence of the two kinds of chiralities, indenyl-based planar chirality and stereogenic centers of the neomenthyl group, was an indispensable factor for inducing high stereoselectivity around the metal center.

ChemInform Abstract: Asymmetric Rh‐Catalyzed Hydrogenation of Enamides with a Chiral 1,4‐Bisphosphine Bearing Diphenylphosphino Groups.

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Enantioposition-selective arylation of biaryl ditriflates by palladium-catalyzed asymmetric Grignard cross-coupling

Asymmetric cross-coupling of achiral biaryl ditriflates with aryl Grignard reagents in the presence of 1 equiv of lithium bromide and 5 mol % of palladium complex PdCl2[(S)-alaphos], where alaphos stands for (2-dimethylamino)propyldiphenylphosphine, gave axially chiral monophenylation products with high enantioposition-selectivity. The remaining triflate group in the monophenylation products was substituted with carboxyl and diphenylphosphino groups through palladium-catalyzed carbonylation and diphenylphosphinylation, respectively.

Synthesis and applications of new chiral diphosphines bearing a diphenylphosphino group and a phenylcyclohexylphosphino group

Chiral diphosphines derived from Diop and BPPM and bearing a phenylcyclohexylphosphinogroup and a diphenylphosphinogroup were prepared. These ligands, and especially the BPPM analog, in association with rhodium complexes, exhibited high enantioselectivities, up to 93%, and activities in the reduction of various unsaturated substrates although they were used as a mixture 50/50 of two epimers.

Asymmetric Rh-Catalyzed Hydrogenation of Enamides with a Chiral 1,4-Bisphosphine Bearing Diphenylphosphino Groups

Much effort has been devoted to the development of efficient asymmetric synthetic methods for the preparation of enantiomerically enriched compounds.1,2 Among various methods for the enantiomerically selective synthesis of chiral organic compounds from prochiral precursors, enantioselective catalytic hydrogenation of dehydro precursors has been extensively developed.3 In fact, asymmetric hydrogenation is one of the most practical methods in asymmetric synthesis, accounting for 70% of all procedures used on a commercial scale.4 However, most asymmetric catalytic hydrogenation systems only hydrogenate electron-deficient olefins with high enantioselectivity and high reactivity. In contrast, electronrich olefins, such as simple enamides5 and enolates,6 are generally poor substrates for asymmetric hydrogenation with most known systems. Since enamides and enolates upon asymmetric hydrogenation can be converted to enantiomerically pure amines and alcohols,7 it would be extremely desirable to have a general and efficient method for this transformation. Recently, Burk and coworkers have reported that Rh complexes bearing the electron-rich DuPhosand BPE-type ligands were efficient catalysts for the asymmetric hydrogenation of enamides8 and enolates.9 They reported that analogous Rh-chiral bisphosphines bearing diphenylphosphino groups (e.g., BINAP, DIOP, and CHIRAPHOS) led to significantly lower enantioselectivities in the reduction of enamides (<60% ee).8 We have been interested in elucidating the steric and electronic effects10 of various diphenylphosphino-bearing chiral ligands in asymmetric hydrogenation processes. Recently a new chiral 1,4-bisphosphine, 2(R),2′(R)-bis(diphenylphosphino)-1(R),1′(R)-dicyclopentane ((R,R)BICP, Figure 1), was reported from our laboratory as an excellent ligand for the Rh-catalyzed asymmetric hydrogenation of dehydroamino acids.11 The key feature of this new ligand is that four stereogenic centers are introduced in a conformationally rigid bicyclic backbone, which is fundamentally different from either axially dissymmetric BINAP or bisphosphines with two stereogenic centers. Herein, we describe the highly enantioselective Rhcatalyzed hydrogenation of enamides using the BICP ligand. Among the known chiral bisphosphines with diphenylphosphino groups, the BICP ligand gives the highest enantioselectivity for the rhodium-catalyzed asymmetric hydrogenation of simple enamides.

Electron ionization-induced fragmentation of diphenylphosphino- and diphenylphosphinoyl-substituted ferrocene derivatives

Electron ionization mass spectra of several diphenylphosphino- and diphenylphosphinoyl-substituted ferrocenes of the general formula [η 5 -C 5 H 4 X)Fe(η 5 -C 5 H 4 Y)], [X/Y = PPh 2 /H (1), P(O)Ph 2 /H (2), PPh 2 /CO 2 H (3), P(O)Ph 2 /CO 2 H (4), PPh 2 /CO 2 CH 3 (5) and P(O)Ph 2 /CO 2 CH 3 (6)1 and of their deuterated analogues IX/Y = PPh 2 /CO 2 D (3a), PPh 2 /CO 2 CD 3 (5a)] are reported. Fragmentation pathways for all compounds studied are presented. The proposed fragmentation schemes are based on accurate mass measurements, observations of metastable ion decompositions and the study of collisionally activated dissociations of important ions. A key role of the ferrocenyl metal centre in the transfer of oxygen-containing groups was confirmed. However, the introduction of another oxophilic group, i.e. trivalent phosphorus of the diphenylphosphino group in the present case, leads to a competition between the two different oxygen acceptors now present in the molecule. If the oxophilicity of the phosphorus atom is saturated by P-oxide formation, the fragmentation pathways change markedly in comparison with those of the parent phosphine. The structure of selected isobaric ions common to the spectra of various compounds is discussed as some of these exhibit different behaviour when originating from fragmentation of different parent molecules.

Enantiospecific nucleophilic substitution of the dimethylamino group in ( R)-tricarbonyl[-{(1-dimethylamino)ethyl}-η 6-benzene]chromium

Treatment of ( R)-tricarbonyl[-{(1-dimethylamino)ethyl}-η 6-benzene]chromium 1 with esters of chloroformic acid leads to enantiospecific substitution of the dimethylamino group for a chloro substituent. The chloro group in turn can enantiospecifically be replaced for a diphenylphosphino group. Both reactions proceed with retention.

Dealkylation of 4-phosphorylated 5-alkoxypyrazoles: Easy synthetic access to P-chloro ylides

The chlorination of 5-alkoxypyrazoles containing bis-(dialkylamino)- or diphenylphosphino groups at the4-position afforded highly unstable chlorophosphoni-um chlorides that dealkylated giving chlorobis(di-alkylamino)- and chlorodiphenylphosphonium(3-methyl-5-oxo-1-phenyl-5H-pyrazol-4-yl)ides. The P-chloro ylides do not react with aromatic aldehydes, but chlorine atoms are easily substituted with OH, NH2 ArNH, and Et2N residues. They also exhibit basic properties and add hydrogen chloride with protonation at N-2. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:41–49, 1998

Synthesis and Structure of P,N-Heterodifunctional Ferrocene Ligands and their Transition Metal Complexes for Palladium-Catalyzed Aryl Amination Reaction

The Staüdinger reaction of the β-ferrocenylvinylazide 1 with di- and triphosphines provided a new range of P,N- heterodifunctional ferrocene ligands bearing an iminophosphorane and at least a diphenylphosphino group; reactivity towards Pd (II) and the ability of the resulting complexes for palladium catalyzed aryl amination reaction is described. © 1997 Elsevier Science Ltd.

Cyclopentadiene with two coordinating sites: 1,5-bis(diphenylphosphino) -2,3,4-trimethylcyclopenta-1,3-diene

The possibility of obtaining the new bidentate 1,2-diphenylphosphinocyclopentadienyl ligand has been studied. 1,5-bis(diphenylphosphino)-2,3,4-trimethylcyclopenta-1,3-diene can be formed from butanone and chlorodiphenylphosphine in eight steps. The results of chemical and spectroscopic studies reveal that a 1.5-sigmatropic migration of the diphenylphosphino group takes place: the 1,2-diphenylphosphino-substituted species are converted into 1.3 species.

Phosphorandiyl-1,3,5-triphosphinane/ Phosphonio-1,3,5-triphosphinin Kationen/ Phosphoranediyl-1,3,5-triphosphinanes / Phosphonio-1,3,5-triphosphinine Cations

Abstract Depending on the reaction conditions, the condensation of triphenylphosphonium bis(trimethylsilyl)methylide 1 with phosphorus trichloride and phosphorus tribromide gives the cyclic trimers (Ph3P=CP-X)3, X = Cl, Br, trihalo-tris(triphenylphosphoranediyl)-1,3,5- triphosphinanes 3 and 5. In solution the compounds dissociate to give the ionic forms 4 and 6 which rapidly exchange the halide between the halophosphine and the phosphenium moieties. The exchange is slowed down when the halide ion is replaced by a tosylate ion. Substitution of the covalent chloride of 4 for diphenylphosphino groups gives again an ionic product 10, while the introduction of a morpholino group as well as the replacement of all chloride by triflate give dicationic compounds 12 and 13. Reaction of 3 with gallium trichloride finally leads to the tris(triphenylphosphonio)-1,3,5-triphosphinine trication as a major equilibrium participant.

Chiral atropisomeric five-membered biheteroaromatic diphosphines: New ligands of the bibenzimidazole and biindole series

Two new chiral atropisomeric biheteroaromatic diphosphines are described: 2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole ( 3a) and 3,3′-dimethyl-1,1′-bis(diphenylphosphino)-2,2′-biindole ( 4a). Structural characterization is given and configurational stability at room temperature demonstrated. The oxidation potential was recognized as a good tool to evaluate the electronic availability of the phosphorus atom in the series of biheteroaromatic diphosphines. Its value increases parallel to the electronic demand of the heterocyclic system and also depends on the position of the diphenylphosphino group.

2-Diphenylphosphino-1,3-diphospholide anions

The title compounds are easily obtained in four steps from 4,5-disubstituted 1,3-diphenyl-1,3-diphosphacyclopent-4-enes ( 1). Metallation of the P CH 2 P unit of 1 followed by reaction with Ph 2PCl allows a diphenylphosphino group to be grafted onto 1 at the C 2 carbon. After removal of the remaining C 2H proton by a base, selective cleavage of the two P 1 Ph and P 3 Ph bonds by lithium in THF affords the corresponding 2-diphenylphosphino-1,3-diphospholide ions ( 5). In one case, the reaction of n-butyllithium with 1a leads to an opening of the five-membered ring via a nucleophilic attack at phosphorus. A bis-(phosphino)methanide ion ( 8) is thus obtained. Its chemistry has been investigated briefly.

Synthesis of bis(diphenylphosphinocyclopentadienyl) yttrium chloride complexes and heterodimetallic derivatives. X-ray structure of bis[(μ-chloro)bis(diphenylphosphinocyclopentadienyl) yttrium(III)

Reaction of lithium diphenylphosphinocyclopentadienide with YCl 3 or YCl 3(THF) 3 and working lead to the formation of three yttrocene phosphines: the lithium metal adduct isolated as (Ph 2PC 5H 4) 2Y(μ-Cl) 2Li(THF) 2 · 0.5 LiCl ( 1), the chloride-bridged dimeric species {(Ph 2PC 5H 4) 2Y(μ-Cl)} 2 ( 2), and the coordinated monometal species [(Ph 2PC 5H 4) 2YCl(THF)] ( 3). The X-ray structure of 2 is remarkable in that the crystal exhibits two independent chloride-bridged dimers that differ in the arrangement ( syn, anti) of the diphenylphosphino groups. Chelation of phosphorus atoms to a molydenum carbonyl moiety is also reported.

Rhodium and Ruthenium Complexes with Optically Active Chelate Cyclopentadienyl-Phosphine Bidentate Ligands

Abstract The first optically active cyclopentadienyl-phosphine bidentate ligands ([Cp-P]H ligands) in which a diphenylphosphino group and a cyclopentadienyl or an indenyl group are connected by an L-threitol derivative or an (S,S)-trans-1,2-dimethylenecyclo-pentane group have been prepared. The rhodium and ruthenium complexes of their anions have been prepared and characterized.