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Novel P,N chelating ligands with three stereogenic centres in positions α to the donor atoms have been prepared in good yields and high enantiomeric purity by a series of reactions beginning with either (R)- or (S)-1-phenylethylamine. These isomers were first lithiated with tBuLi and converted into aminophosphanes 3a by treatment with (Et2N)2PCl. They were transformed into the enantiomeric primary phosphanes 4 by quantitative solvolysis with ethanol to give the phosphonous acid esters 3b and subsequent reduction with LiAlH4. Stepwise treatment of 4 with nBuLi and the cyclic sulfate of (S,S)-2,5-hexanediol gave the isomeric tertiary phosphanes (R,RR)-5 and (S,RR)-5. Treatment of the aminophosphane (R)-3a with (R)-2,2′-binaphthol yielded the aminophosphonite (R,R)-6 in high yields. Cationic (COD)Rh complexes of 5 were prepared by treatment with [Rh(COD)Cl]2, the PF6− salts 7a being isolated. Analogous (2,5-norbornadiene)Rh complexes 7b were prepared similarly. The chelate nature of the P,N ligands in these salts is indicated by their NMR spectra in solution and is confirmed by the crystal structures of (R,RR)-7a and (S,RR)-7a. With the exception of (S,RR)-7a, the complexes 7a and 7b are shown to catalyse the asymmetric hydrogenation of methyl acetamidocinnamate at room temperature. Differences in the catalytic activity of the complexes are related to the different dynamic behaviour detected by the 1H EXSY spectra for the COD ligands of 7a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Reaction of 2,2'-difluoro-1,1'-biphenyl with chlorosulfonic acid and subsequent hydrolysis followed by neutralization with potassium or sodium hydroxide affords disodium or dipotassium 5,5'-disulfonato-2,2'-difluoro-1,1'-biphenyl (1a, 1b). On treatment of 1b with diphenyl- or phenylphosphine in the superbasic medium DMSO/KOH, phosphine ligand 2 or 3 with a disulfonated 1,1'-biphenyl backbone or a dibenzophosphole moiety is formed. The structure of the oxide of 5-phenyldibenzophosphole 3, which crystallizes as 4.2.5H(2)O in the monoclinic space group P2(1)/n with a = 13.799(3) A, b = 19.246(4) A, c = 17.764(4) A, beta = 105.63(3) degrees, and Z = 4, has been determined by X-ray analysis. Nucleophilic phosphination of 1a with NaPH(2) in liquid ammonia yields the sodium phosphide 5a which on protonation gives the water-soluble 5H-dibenzophosphole 5. Reaction of 1b with PH(3) in the superbasic medium DMSO/KOtBu affords 5b in addition to the oxidation product 6a. On oxidation of 5a or 5b with H(2)O(2), the sodium or potassium salts of the sulfonated phosphinic acids 6a or 6b, respectively, are formed. Alkylation of the sodium dibenzophospholide 5a with 2,2'-bis(chloromethyl)-1,1'-biphenyl or 1,4-di-O-p-toluenesulfonyl-2,3-O-isopropylidene-D-threitol yields the chiral water-soluble bidentate phosphine ligands 8 and 9, respectively.

Phosphine ligands containing mono- and multiply substituted aromatic substituents (1–13, 19a and 19b) are accessible in high yields by palladium-catalyzed PC coupling reactions between primary, secondary or disecondary phosphines and iodo- or bromoaromatic compounds. The reaction is of broad applicability and compatible with electron donor or electron acceptor substituents in ortho, meta or para position to the halogen in the aromatic ring systems. It may be performed in protic and aprotic solvents. The chiral spirocyclic boronato complex 15a is formed upon reaction of 3 with boric acid, while with benzeneboronic acid 15c with a peripheral Lewis acid group is obtained. The Pd-mediated PC coupling reaction of primary phosphines proceeds stepwise, tailor-made chiral secondary (16) and tertiary phosphines (17) being formed in high yields. Through combination with Suzuki-type CC coupling reactions, the scope of Pd-catalyzed PC coupling may be extended further, with novel ligands (20a, 20b, 21a, 21b) with biphenylyl substituents being accessible. The X-ray structures of the salicylic acid derivative 3 (space group P 1 ) and of ortho-iso-propylphenyl-diphenylphosphine 6 (space group Pbca) have been determined.

Base catalyzed addition of 1-vinylimidazole to primary and secondary phosphines affords tertiary phosphines with terminal 1-imidazolyl substituents C3H3N2 in high yields. The X-ray structure of the oxide Ph2P(O)–(CH2)2–1-C3H3N2 has been determined (space group P 1 ). By selective N-protonation and protected group N-quaternization novel cationic phosphines, e.g. 2a, 2b, 9 and 10, with peripheral 1-imidazolium groups are obtained. These are interesting ligands for catalytic reactions in biphasic systems containing ionic liquids as polar phase and may be employed in hydroformylation of long-chain olefins like 1-octene.

Phosphino derivatives of serine R2P–CH2–CH(NHBOC)(COOMe) (2 a–2 d) have been obtained in high yield by nucleophilic phosphination of N-(tert.butoxycarbonyl)-3-iodo-L-alanine methylester with secondary phosphines R2PH (R = Ph, 2-tolyl, 3,5-xylyl, cyclohexyl) in DMF using potassium carbonate as the base. Deprotection of 2 b with HCl affords the amino acid ester hydrochloride [2-Tol2P–CH2–CH(NH3)(COOMe)]+Cl– (3 a). The X-ray structures of 2 a (space group P21/n) and 2 c (space group P 1) have been determined. The two enantiomers of 2 a or 2 c are interconnected by N–H…O hydrogen bridges forming dimers in the solid state. Chirale Phosphinliganden aus Aminosauren. II. Eine einfache Synthese von Phosphinoserinen durch nucleophile Phosphinierungsreaktionen – Rontgenstrukturanalysen von Ar2P–CH2–CH(NHBOC)(COOMe) (Ar = Ph, m-Xylyl) Phosphinoderivate von Serin R2P–CH2–CH(NHBOC)(COOMe) (2 a–2 d) sind in hohen Ausbeuten durch nucleophile Phosphinierung von N-(tert.butoxycarbonyl)-3-iod-L-alaninmethylester mit sekundaren Phosphinen R2PH (R = Ph, 2-Tolyl, 3,5-Xylyl, Cyclohexyl) in DMF unter Verwendung von Kaliumcarbonat als Base auf einfache Weise zuganglich. Die Abspaltung der Schutzgruppe BOC mit HCl in 2 b liefert das Aminosaureesterhydrochlorid [2-Tol2P–CH2–CH(NH3)(COOMe)]+Cl– (3 a). Die Rontgenstrukturanalysen von 2 a (Raumgruppe P21/n) und 2 c (Raumgruppe P 1) wurden durchgefuhrt. Im Festkorper sind die beiden Enantiomeren von 2 a bzw. 2 c durch N–H…O-Wasserstoffbrucken unter Bildung von Dimeren miteinander verknupft.

Reaction of 2-(diphenylphosphino)phenylphosphonous acid tetramethyldiamide 1 with (+)-menthol, (1S,2S,3S,5R)-isopinocampheol and (1R,2R)-trans-cyclohexanediol affords enantiopure phosphino-phosphonite ligands 3–5. The X-ray structures of 1 (space group P21/n) and 3 (space group P21) have been determined. The reaction of 1 with (1R,2R,3S,5R)-(−)-pinanediol proceeds diastereoselectively to afford a novel type of enantiopure phosphino-phosphonite ligand 6 with an asymmetric substituted P atom. On reaction of (+)-cedryl alcohol with 1 the adduct 7 of the phosphonous acid 2-Ph2PC6H4P(O)(H)OH 9 and its dimethylammonium salt is formed through elimination of water and subsequent hydrolysis. The structure of 7 (space group P1) was elucidated by X-ray structural analysis. Reduction of the chlorophosphine 8 with LiAlH4 yields the novel primary–tertiary phosphine 10, which is a valuable starting material for the synthesis of the enantiopure C1 symmetric bidentate phospholane ligands 11 and 12.

The dilithium salt 1a formed by ortho-metallation of N-tert-butoxycarbonylaniline (BOC-aniline) 1 with two equivalents of tert-butyllithium reacts with the chlorophosphines Ph3-nPCln (n = 1 -3) to yield the BOC protected ortho-aminophenylphosphines 2 - 4 in high yields. On deprotection of 2 - 4 with trimethylchlorosilane in the presence of phenol the HCl adducts of the ortho-aminophenylphosphines 5 -7 are formed which may be deprotonated with KOH or NaOH to give the neutral phosphines 5a -7a. The novel secondary phosphine 8 with two ortho-aminophenyl groups is accessible by cleavage of the P-C bond in 7a with metallic lithium and subsequent hydrolysis. The bifunctional P,N ligands 6 or 6a are alternatively accessible by Pd-catalyzed P-C coupling of ortho-iodoaniline with phenylphosphine. If a 1:1 stoichiometry is employed in the coupling reaction of ortho-iodoaniline and phenylphosphine the chiral secondary phosphine 9 is formed.

The title compound, C(2)H(7)N(4)O(+).CH(4)O(3)P(-).H(2)O, crystallized with one carbamoylguanidinium cation, one methylphosphonate anion and one water molecule in the asymmetric unit. All H atoms of the carbamoylguanidinium ion are involved in a hydrogen-bonded network. The CH(3)PO(2)(OH) anions, together with the water molecules, build O-H...O hydrogen-bonded ribbons around a 2(1) screw axis parallel to the b axis. Neighbouring ribbons are not directly connected via hydrogen bonding. The carbamoylguanidinium cations are linked to these ribbons by N-H...O bridges and build a slightly buckled layer structure, the interlayer distance being b/2.

New guanidinium-modified diphosphine ligands with a xanthene backbone show high overall activity and high regioselectivity in the biphasic hydroformylation of oct-1-ene using hexafluorophosphate ionic liquids.