Fluorescent aminoarylcyclotetraphosphazenes

In the present work, octachlorocyclotetraphosphazatetraene (1), N₄P₄Cl₈, is reacted with aniline (2), 1-napthylamine (4) and 2-aminoanthracene (6) to give octakis(arylamino)cyclotetraphosphazenes (3, 5 and 7). These cyclotetraphosphazene compounds (3, 5 and 7) have been fully characterized by elemental analysis, mass (MS), FT-IR, ¹H and ³¹P NMR spectroscopies. The molecular and crystal structures of 5 have been characterized by X-ray crystallography. The structure of 5 is monoclinic with the space group P21/c. The octakis(1-napthylamino)-(5) and octakis(2-aminoanthracene)-(7) cyclotetraphosphazene compounds have been synthesised for the first time in this study. The fluorescence properties of 3, 5 and 7 have been investigated in tetrahydrofuran (THF) and have been shown to have highly fluorescence behavior. This work also presents the quenching of arylamino substituted cyclotetraphosphazene derivatives (3, 5 and 7) by p-benzoquinone (BQ) or hydroquinone (HQ).     

An efficient microwave assisted synthesis of novel class of Rhodanine derivatives as potential HIV-1 and JSP-1 inhibitors

(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-phenyl-2-thioxothiazolidin-4-one (7a-q) derivatives have been synthesized by the condensation reaction of 3-phenyl-2-thioxothiazolidin-4-ones (3a-h) with suitably substituted 2-(1H-indol-3-yl)-2-oxoacetaldehyde (6a-d) under microwave condition. The thioxothiazolidine-4-ones were prepared from the corresponding aromatic amines (1a-e) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a-h) were synthesized from the corresponding acid chlorides (5a-d) using HSnBu₃.     

Syntheses and structures of iron carbonyl complexes derived from N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine and N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine

The reaction of N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine (1) with Fe₂(CO)₉ in refluxing acetonitrile yielded di-(μ₃-thia)nonacarbonyltriiron (2), μ-[N-(5-methyl-2-thienylmethyl)-η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido]hexacarbonyldiiron (3), and N-(5-methyl-2-thienylmethylidene)amine (4). If the reaction was carried out at 45 °C, di-μ-[N-(5-methyl-2-thienylmethylidene)-η¹(N);η¹(S)-2-thiolethylamino]-μ-carbonyl-tetracarbonyldiiron (5) and trace amount of 4 were obtained. Stirring 5 in refluxing acetonitrile led to the thermal decomposition of 5, and ligand 1 was recovered quantitatively. However, in the presence of excess amount of Fe₂(CO)₉ in refluxing acetonitrile, complex 5 was converted into 2-4. On the other hand, the reaction of N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine (6) with Fe₂(CO)₉ in refluxing acetonitrile produced 2, μ-[N-(6-methyl-2-pyridylmethyl)-η¹ (N_py);η¹:η¹(N); η¹:η¹(S)-2-thiolatoethylamido]pentacarbonyldiiron (7), and μ-[N-(6-methyl-2-pyridylmethylidene)-η²(C,N);η¹:η¹(S)-2- thiolethylamino]hexacarbonyldiiron (8). Reactions of both complex 7 and 8 with NOBF₄ gave μ-[(6-methyl-2-pyridylmethyl)-η¹(N_py);η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido](acetonitrile)tricarbonylnitrosyldiiron (9). These reaction products were well characterized spectrally. The molecular structures of complexes 3, 7-9 have been determined by means of X-ray diffraction. Intramolecular 1,5-hydrogen shift from the thiol to the methine carbon was observed in complexes 3, 7, and 9.     

Total synthesis of apigenin 7,4′-di-O-β-glucopyranoside, a component of blue flower pigment of Salvia patens, and seven chiral analogues

We have succeeded in the first total synthesis of apigenin 7,4′-di-O-β-d-glucopyranoside (1a), a component of blue pigment, protodelphin, from naringenin (2). Glycosylation of 2 according to Koenigs-Knorr reaction provided a monoglucoside 4a in 80% yield, and this was followed by DDQ oxidation to give apigenin 7-O-glucoside (12a). Further glycosylation of 4′-OH of 12a with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl fluoride (5a) was achieved using a Lewis acid-and-base promotion system (BF₃·Et₂O, 2,6-di-tert-butyl-4-methylpyridine, and 1,1,3,3-tetramethylguanidine) in 70% yield, and subsequent deprotection produced 1a. Synthesis of three other chiral isomers of 1a, with replacement of d-glucose at 7 and/or 4′-OH by l-glucose (1b-d), and four chiral isomers of apigenin 7-O-β-glucosides (6a,b) and 4′-O-β-glucosides (7a,b) also proved possible.     

Regio- and stereoselective reactions of a rhodanine derivative with optically active 2-methyl- and 2-phenyloxirane

The reaction of a rhodanine derivative (=(Z)-5-benzylidene-3-phenyl-2-thioxo-1,3-thiazolidin-4-one; 1) with (S)-2-methyloxirane (2) in the presence of SiO₂ in dry CH₂Cl₂ for 10 days led to two diastereoisomeric spirocyclic 1,3-oxathiolanes 3 and 4 with the Me group at C(2) (Scheme 2). The analogous reaction of 1 with (R)-2-phenyloxirane (5) afforded also two diastereoisomeric spirocyclic 1,3-oxathiolanes 6 and 7 bearing the Ph group at C(3) (Scheme 3). The structures of 3, 4, 6, and 7 were confirmed by X-ray crystallography (Figs. 1 and 2). These results show that oxiranes react selectively with the thiocarbonyl group (CS) in 1. Furthermore, the nucleophilic attack of the thiocarbonyl S-atom at the SiO₂-activated oxirane ring proceeds with high regio- and stereoselectivity via an S_N2-type mechanism.     

Synthesis and characterization of aluminum and zinc complexes supported by pyrrole-based ligands and catalysis of the aluminum complexes toward the ring-opening polymerization of ?-caprolactone

Reaction of quinolin-8-amine with 1H-pyrrole-2-carbaldehyde or 5-tert-butyl-1H-pyrrole-2-carbaldehyde catalyzed by HCO₂H forms N-((1H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL, 3a) or N-((5-tert-butyl-1H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL′, 3b). Treatment of 3a and 3b respectively with AlMe₃ or AlEt₃ in toluene affords corresponding aluminum complexes LAlMe₂ (4a), L′AlMe₂ (4b) and LAlEt₂ (4c). Reaction of 3a and 3b with an equivalent of ZnEt₂ in toluene generates L₂Zn and L′₂Zn, respectively. A related compound N-((1H-pyrrol-2-yl)methylene)-2-(3,5-dimethyl-1H-pyrazol-1-yl)benzenamine (≡ HL″, 7) was prepared by reaction of 2-(3,5-dimethyl-1H-pyrazol-1-yl)benzenamine with 1H-pyrrole-2-carbaldehyde in the presence of HCO₂H. Reaction of 7 with AlMe₃ gives L″₂AlMe (8), and with ZnEt₂ yields L″₂Zn (9). All new compounds were characterized by NMR spectroscopy and elemental analysis. The structures of complexes 4b, 5b and 8 were additionally characterized by single crystal X-ray diffraction analyses. Complexes 4a-4c, and 8 were proved to be active catalysts for the ring-opening polymerization (ROP) of ?-caprolactone (?-CL) in the presence of BnOH. The kinetic study of the polymerization reactions catalyzed by 4a and 8 was performed.     

Sodium dithionite initiated addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to β-pinene: Synthesis of CF3-substituted terpenoids

Sodium dithionite effectively promotes the addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to the exocyclic double bond of β-pinene. The reaction proceeded in an MeCN/H₂O system to give almost quantitatively a 1:1 mixture of diastereoisomers of 4-(2-bromoisopropyl)-1-(2-chloro-3,3,3-trifluoropropyl)-cyclohexene (1). Dehydrobromination of 1 with pyridine gave a mixture of regioisomeric dienes 2 and 3, while treatment with DBU at elevated temperature resulted in total dehydrohalogenation to give trienes 4 and 5. Reduction of 1 with Bu₃SnH gave 1-(2-chloro-3,3,3-trifluoropropyl)-4-(isopropyl)cyclohexene (6) which on dehydrochlorination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afforded conjugated diene, 4-isopropyl-1-(trans-3,3,3-trifluoropropenyl)-cyclohexene (7), with 50% overall yield. All the transformations proceeded with the retention of configuration at the carbon atom C-4 and the final compound 7 exhibited high optical activity.     

Synthesis and structural characterization of 1′-(diphenylphosphino)ferrocene-1-carboxamide, its corresponding hydrazide, some heterocycles derived from the hydrazide and palladium(II) complexes with these functional phosphinoferrocene ligands

Two polar phosphinoferrocene ligands, 1′-(diphenylphosphino)ferrocene-1-carboxamide (1) and 1′-(diphenylphosphino)ferrocene-1-carbohydrazide (2), were synthesized in good yields from 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) via the reactive benzotriazole derivative, 1-[1′-(diphenylphosphino)ferrocene-1-carbonyl]-1H-1,2,3-benzotriazole (3). Alternatively, the hydrazide was prepared by the conventional reaction of methyl 1′-(diphenylphosphino)ferrocene-1-carboxylate with hydrazine hydrate, and was further converted via standard condensation reactions to three phosphinoferrocene heterocycles, viz 2-[1′-(diphenylphosphino)ferrocen-1-yl]-1,3,4-oxadiazole (4), 1-[1′-(diphenylphosphino)ferrocen-1-carbonyl]-3,5-dimethyl-1,2-pyrazole (5), and 1-[1′-(diphenylphosphino)ferrocene-1-carboxamido]-3,5-dimethylpyrrole (6). Compounds 1 and 2 react with [PdCl₂(cod)] (cod = η²:η²-cycloocta-1,5-diene) to afford the respective bis-phosphine complexes trans-[PdCl₂(L-κP)₂] (7, L = 1; 8, L = 2). The dimeric precursor [(L^NC)PdCl]₂ (L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹) is cleaved with 1 to give the neutral phosphine complex [(L^NC)PdCl(1-κP)] (9), which is readily transformed into a ionic bis-chelate complex [(L^NC)PdCl(1-κ²O,P)][SbF₆] (10) upon removal of the chloride ligand with Ag[SbF₆]. Pyrazole 5 behaves similarly affording the related complexes [(L^NC)PdCl(5-κP)] (12) and [(L^NC)PdCl(5-κ²O,P)][SbF₆] (13), in which the ferrocene ligand coordinates as a simple phosphine and an O,P-chelate respectively, while oxadiazole 4 affords the phosphine complex [(L^NC)PdCl(4-κP)] (11) and a P,N-chelate [(L^NC)PdCl(4-κ²N³,P)][SbF₆] (14) under similar conditions. All compounds were characterized by elemental analysis and spectroscopic methods (multinuclear NMR, IR and MS). The solid-state structures of 1⋅½AcOEt, 2, 7⋅3CH₃CN, 8⋅2CHCl₃, 9⋅½CH₂Cl₂⋅0.375C₆H₁₄, 10, and 14 were determined by single-crystal X-ray crystallography.     

Sodium dithionite initiated regio- and stereoselective radical addition of polyfluoroalkyl iodide with norbornene analogs

Sodium dithionite initiated free-radical addition of polyfluoroalkyl iodides (2m-2s) with norbornene 1a and its derivatives, such as norbornene-2-carboxylates 1b and 1c, and norbornene-2-carboxylic acids 1d and 1e was investigated. In all the cases, the addition of R_F group was stereoselectively delivered at exo-position and the predominant configuration of products was trans. Under the similar condition, norbornene-2-carboxylic ethyl ester 1b reacted with 2p to give 6-exo-R_F-5-endo-iodo adduct 3bp and 5-exo-R_F-6-endo-iodo adduct 5bp in the ratio of 4:1. While 1c, which has a heavy crowded group in the 2-endo-position, gave 6-exo-R_F-5-endo-iodo adduct 3cp and polyfluoroalkylated product 4cp retaining the trans-configuration and the exo-orientation of R_F group. The fluoroalkylation-lactonization reaction occurred in the reaction of norbornene-2-endo-carboxylic acids 1d and 1e with polyfluoroalkyl iodides to afford the corresponding fluoroalkylated γ-lactone products (7dp-7ds, and 7em-7er). The configuration of the products was further confirmed by 2D NMR and X-ray diffraction analyses for the first time.     

First cross-coupling reactions on halogenated 1H-1,2,4-triazole nucleosides

The halogenated 1H-1,2,4-triazole glycosides 6-10 were synthesized by BF₃-activated glycosylation of 3(5)-chloro-1,2,4-triazole (2), 3,5-dichloro-1,2,4-triazole (3), 3,5-dibromo-1,2,4-triazole (4), and 3(5)-bromo-5(3)-chloro-1,2,4-triazole (5) with 1,2,3,4-tetra-O-pivaloyl-β-d-xylopyranose (1). The β-anomeric major products 3-chloro-1-(2,3,4-tri-O-pivaloyl-β-d-xylopyranosyl)-1,2,4-triazole (6β), 3,5-dichloro-1-(2,3,4-tri-O-pivaloyl-β-d-xylopyranosyl)-1,2,4-triazole (7β), and 3,5-dibromo-1-(2,3,4-tri-O-pivaloyl-β-d-xylopyranosyl)-1,2,4-triazole (8β) were used as starting materials for transition metal catalyzed C-C-coupling reactions. Arylations of the triazole ring of 7β, and 8β were successful in 5-position with phenylboronic acid, 4-vinylphenylboronic acid, and 4-methoxyphenylboronic acid, respectively, under Suzuki cross-coupling conditions (products 11-17). Moreover, a Cu-catalyzed perfluoroalkylation of 8β is reported with 1-iodo-perfluorohexane yielding 3-perfluorohexyl-1-(2,3,4-tri-O-pivaloyl-β-d-xylopyranosyl)-1,2,4-triazole (18). Compound 18 was depivaloylated to the trihydroxy derivative 19. The copper-mediated reaction of 8β with Rupert's reagent gave the bis(3-bromo-1-(2,3,4-tri-O-pivaloyl-β-d-xylopyranosyl)-1,2,4-triazol-5-yl) (20).     

Dipheno-silyliminoquinones - A 14π-system

Lithium salts of 2.6-dialkylanilines react with di-tert-butylfluorosilanes to give mono (1-3) - and bis (7, 8)-(2.6-dialkylphenylamino)silanes. Amino-2.6-dimethylphenyl-(di-tert-butylfluoro)silane (1) forms with BuLi a dimeric lithium salt (4) containing an eight-membered (LiFNSi)₂ ring system. Thermally, 4 loses LiF and a bicyclic compound (9) via iminosilenes is obtained. The lithium salt of the bulkier amino-2.6-diisopropylphenyl-(di-tert-butylfluorosilanes) (5-7) thermally loses LiH and iminosilanes (10-12) with a 14π-system are isolated. The reaction mechanisms and crystal structures are discussed.     

Synthesis of l-azaisotryptophan and its analogs: a general access to new 2-substituted azaindoles

l-(N-Cbz)-7-azaisotryptophan, l-(N-Cbz)-1a, a new isostere of tryptophan, was synthesized by reacting Li₂-(N-Boc)-2-amino-3-picoline, Li₂-(N-Boc)-2a, with appropriately protected l-aspartic acid followed by simple functional group manipulation. This synthetic success led us to access a set of analogs of azaisotryptophan (4a–c; 6a–c) as well as a new class of chiral amines (7a–c; 8a–c) for future application in asymmetric synthesis and design of homochiral ligands. Further, we have generalized the method substantiating a variety of new azaindol-2-yl derivatives (10aa–10lc) with functionalized substituents. In a preliminary luminescence characterization, l-(N-Cbz)-1a has exhibited about 30 nm bathochromic shifted fluorescence emission compared to tryptophan and (N-Cbz)-tryptophan.     

Half sandwich complexes of Ru(II) and complexes of Pd(II) and Pt(II) with seleno and thio derivatives of pyrrolidine: Synthesis, structure and applications as catalysts for organic reactions

The reactions of PhSe⁻, PhS⁻ and Se²⁻ with N-{2-(chloroethyl)}pyrrolidine result in N-{2-(phenylseleno)ethyl}pyrrolidine (L1), N-{2-(phenylthio)ethyl}pyrrolidine (L2), and bis{2-pyrrolidene-N-yl)ethyl selenide (L3), respectively, which have been explored as ligands. The complexes [PdCl₂(L1/L2)] (1/7), [PtCl₂(L1/L2)] (2/8), [RuCl(η⁶-C₆H₆)(L1/L2)][PF₆] (3/9), [RuCl(η⁶-p-cymene)(L1/L2)][PF₆] (4/10), [RuCl(η⁶-p-cymene)(NH₃)₂][PF₆] (5) and [Ru(η⁶-p-cymene)(L1)(CH₃CN)][PF₆]₂·CH₃CN (6) have been synthesized. The L1-L3 and complexes were found to give characteristic NMR (Proton, Carbon-13 and Se-77). The crystal structures of complexes 1, 3-6, 9 and 10 have been solved. The Pd-Se and Ru-Se bond lengths have been found to be 2.353(2) and 2.480(11)/2.4918(9)/2.4770(5) Å, respectively. The complexes 1 and 7 have been explored for catalytic Heck and Suzuki-Miyaura coupling reactions. The value of TON has been found up to 85 000 with the advantage of catalyst’s stability under ambient conditions. The efficiency of 1 is marginally better than 7. The Ru-complexes 3 and 9 are good for catalytic oxidation of primary and secondary alcohols in CH₂Cl₂ in the presence of N-methylmorpholine-N-oxide (NMO). The TON value varies between 8.0 × 10⁴ and 9.7 × 10⁴ for this oxidation. The 3 is somewhat more efficient catalyst than 9.     

Synthesis and structural characterization of rac-2-[(diphenylphosphino)methyl]ferrocenecarboxylic acid, its selected derivatives and some rhodium complexes

rac-2-[(Diphenylphosphino)methyl]ferrocenecarboxylic acid (1) was prepared in a good yield from rac-2-(N,N-dimethylaminomethyl)bromoferrocene (2) via rac-2-(hydroxymethyl)bromoferrocene (4) and rac-2-[(diphenylphosphino)methyl]bromoferrocene (5), and further converted to the respective phosphine oxide (6), phosphine sulfide (7) and methyl ester (8). The phosphines 1 and 8 were studied as ligands in rhodium complexes. The reaction of di-μ-chloro-bis[chloro-(η⁵-pentamethylcyclopentadienyl)rhodium(III)] with the stoichiometric amounts of 1 and 8 yielded the corresponding mononuclear complexes with P-monodentate ligands: [RhC₂(η⁵-C₅Me₅)(L-κP)], 9 and 10, respectively. Attempted deprotonation of 9 with LiBu or KOt-Bu gave intractable mixtures, in which the parent complex 9 as the major component was accompanied by two new compounds, likely the diastereoizomeric phosphinocarboxylate complexes. A defined O,P-chelating phosphinocarboxylate complex, [SP-4-2]-carbonyl-[rac-2-{(diphenylphosphino)methyl}ferrocenecarboxylato-κ²O,P]-tricyclohexylphosphinerhodium(I) (12), was obtained from the displacement of acetylacetonate(1−) (acac) ligand in [Rh(acac)(CO)(PCy₃)] (Cy = cyclohexyl) with acid 1. The structures of 1, 6 · CHCl₃, and 7 · 1/2 CH₂Cl₂, 10, and hydrated complexes 9 and 12 were determined by single-crystal X-ray diffraction.     

Base-induced cyclizations. Reactions of the 1-halo-6-(2-hydroxyethoxy)-cyclohexenes with potassium t-butoxide

Reactions of 1-bromo-6-(2-hydroxyethoxy)cyclohexene (2) and its chloro analog 3 with potassium t-butoxide in dimethyl sulfoxide at 60–70° gave cyclohex-2-enone ethylene ketal (7) and cis-2,5-dioxabicyclo[4.4.0]dec-7-ene (8) as the major products. Under these conditions, 1-(2-hydroxyethoxy)-1,4-cyclohexadiene (13) is also converted to 7 and elimination products, benzene and ethylene glycol. Conversion of 13 to 7 was shown to be reversible by examination of 7 that had been treated with t-BuOK. in DMSO-d₆. In tetrahydrofuran, 2 and t-BuOK gave benzene as a major product, together with small amounts of 2,5-dioxabicyclo[4.4.0]-dec-6-ene (6), 7, and 8. Mechanisms are proposed for these substitution reactions.     

Oxovanadium(IV) complexes as molecular catalysts in epoxidation: Simple access to pyridylalkoxide derivatives

Reaction of bis(aryl)-2-pyridylmethanol ligands (1a-7a) with VO(SO₄) · 5H₂O results in the formation of metal-oxo complexes [VO(N-O)₂] (1-7), with N-O = bis(aryl)-2-pyridylmethanol. A molecular structure of (4) has been determined by single crystals X-ray diffraction study, which showed the expected square planar pyramidal geometry with the pyridine ring nitrogens in trans-position to each other. The metal-oxo complexes (1-4,6,7) demonstrated the ability to catalyse epoxidation reactions of alkenes with molecular oxygen.     

A unique peroxide formation based on the Mn(III)-catalyzed aerobic oxidation

The autoxidation of a mixture of 1,1-diarylsubstituted alkenes 4 and 4-hydroxy-1H-quinolin-2-ones 5 in the presence of a catalytic amount of manganese(III) acetate dihydrate in air gave 3,3-bis(2-hydroperoxyethyl)-1H-quinoline-2,4-diones 6 in 31-91% yields together with [4.4.3]propellane-type cyclic peroxides 7 (10-34%). A similar aerobic oxidation of 3-substituted quinolinones 8 yielded cyclic peroxide derivatives 9 and/or 3-hydroperoxyethylated quinolinediones 10 depending on the substituent. The structures of the bis(hydroperoxide) 6 (R¹=Me, Ar=4-ClC₆H₄) and the [4.4.3]propellane 7 (R¹=Me, Ar=Ph) have been corroborated by X-ray crystallography.     

Ring-opening metathesis polymerization (ROMP) of N-cycloalkyl-7-oxanorbornene dicarboximides by well-defined ruthenium initiators

Ring-opening metathesis polymerization (ROMP) of exo-N-(1-adamantyl)-7-oxanorbornene-5,6-dicarboximide (AdONDI) (3a), exo-N-cyclohexyl-7-oxanorbornene-5,6-dicarboximide (ChONDI) (3b) and exo-N-phenyl-7-oxanorbornene-5,6-dicarboximide (PhONDI) (3c) using well-defined alkylidene ruthenium catalysts (PCy₃)₂(CI)₂RuCHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy₃)CI₂RuCHPh (II) was studied. The catalysts I and II gave polymers with around 70% and 50% trans vinylene content, respectively. The homopolymer of 3a had a T_g of 198 °C, while poly-3b showed a T_g of 122 °C. Copolymers of 3a, 3b and 3c with norbornene (NB) showed significant T_g increases over poly-NB.     

Synthetic access to optically active isoflavans by using allylic substitution

A general approach to the (S)- and (R)-isoflavans was invented, and efficiency of the method was demonstrated by the synthesis of (S)-equol ((S)-3), (R)-sativan ((R)-4), and (R)-vestitol ((R)-5). The key step is the allylic substitution of (S)-6a (Ar¹=2,4-(MeO)₂C₆H₃) and (R)-6b (Ar¹=2,4-(BnO)₂C₆H₃) with copper reagents derived from CuBr·Me₂S and Ar²-MgBr (7a, Ar²=4-MeOC₆H₄; 7b, 2,4-(MeO)₂C₆H₃; 7c, 2-MOMO-4-MeOC₆H₃), furnishing anti S_N2′ products (R)-8a and (S)-8b,c with 93-97% chirality transfer in 60-75% yields. The olefinic part of the products was oxidatively cleaved and the Me and Bn groups on the Ar¹ moieties was then removed. Finally, phenol bromide 9a and phenol alcohols 9b,c underwent cyclization with K₂CO₃ and the Mitsunobu reagent to afford (S)-3 and (R)-4 and -5, respectively.     

Chiral cyclopentadienyl ruthenium(II) complexes with P,P-ligands derived from (1R,2R)-1,2-diaminocyclohexane: Synthesis,crystal structures and catalytic activity in Diels–Alder reactions

Chiral cyclopentadienyl ruthenium(II) complexes [CpRu(L1–L3)Cl] (5–7) have been prepared by reaction of [CpRu(PPh₃)₂Cl] with chiral P,P-ligands (1R,2R)-1,2-bis(diphenylphosphinamino)cyclohexane (L1), N,N′-[bis-(3,3′-bis-tert-butyl-5,5′-bis-methoxy-1,1′-biphenyl-2,2′-diyl)phosphite]-(1R,2R)-1,2-diaminocyclohexane (L2) and N,N′-[bis-(R)-1,1′-binaphtyl-2,2′-diyl)phosphite]-(1R,2R)-1,2-diaminocyclohexane (L3). The molecular structures of 5 and 6 have been determined by single-crystal X-ray analysis. Studies on catalytic activity of the cations derived from (5–7) by treatment with AgSbF₆, are also reported.