Palladium-catalyzed asymmetric synthesis of allylic alcohols from unsymmetrical and symmetrical racemic allylic carbonates featuring C-O-bond formation and dynamic kinetic resolution

Described is the asymmetric synthesis of the allylic alcohols 11 (85% ee), 15 (99% ee), 17 (93% ee), 19 (61% ee), and 21 (69% ee) through a Pd-catalyzed reaction of the unsymmetrical carbonates rac-10, rac-12, rac-14, rac-16, rac-18, and rac-20, respectively, with KHCO₃ and H₂O in the presence of bisphosphane 6. Similarly the allylic alcohols 23 (99% ee) and 25 (97% ee) have been obtained from the symmetrical carbonates rac-22 and rac-24, respectively. Reaction of the meso-biscarbonate 26 with H₂O and Pd(0)/6 afforded alcohol 27 (96% ee), which was converted to the PG building block 32. The unsaturated bisphosphane 33 showed in the synthesis of alcohols 36, 37, and 39 a similar high selectivity as 6. The formation of alcohols 11, 15, and 17 involves an efficient dynamic kinetic resolution.     

Supramolecular nanostructured assemblies of different types of porphyrins with fullerene using TiO2 nanoparticles for light energy conversion

TiO₂ nanoparticles were modified with porphyrin derivatives, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (Ar-H₂P-COOH), 5-[4-benzoic acid]-10,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H-H₂P-COOH), and 5,10,15,20-tetra[4-benzoic acid]-21H,23H-porphyrin (H₂P-4COOH). The porphyrin-modified TiO₂ nanoparticles were deposited on nanostructured OTE/SnO₂ electrode together with nanoclusters of fullerene (C₆₀) in acetonitrile-toluene (3/1, v/v) using an electrophoretic deposition technique to afford the porphyrin-modified TiO₂ composite electrode denoted as OTE/SnO₂/(porphyrin-modified TiO₂ nanoparticle+C₆₀)_n. The porphyrin-modified TiO₂ composite electrodes have efficient light absorbing properties in the visible region, exhibiting the photoactive response under visible light excitation using redox couple. The incident photon-to-photocurrent efficiency (IPCE) values of supramolecular nanostructured electrodes of porphyrin-modified TiO₂ nanoparticles with fullerene [OTE/SnO₂/(Ar-H₂P-COO-TiO₂+C₆₀)_n, OTE/SnO₂/(H-H₂P-COO-TiO₂+C₆₀)_n, and OTE/SnO₂/(H₂P-4COO-TiO₂+C₆₀)_n] are much larger than those of the reference systems of porphyrin-modified TiO₂ nanoparticles without C₆₀ [OTE/SnO₂/(Ar-H₂P-COO-TiO₂)_n, OTE/SnO₂/(H-H₂P-COO-TiO₂)_n, and OTE/SnO₂/(H₂P-4COO-TiO₂)_n]. In particular, the maximum IPCE value (41%) is obtained for OTE/SnO₂/(H-H₂P-COO-TiO₂+C₆₀)_n under the bias potential of 0.2 V versus SCE. This indicates that the formation of supramolecular complexes between porphyrins and fullerene on TiO₂ nanoparticles plays an important role in improvement of the light energy conversion properties.     

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.     

Synthesis and properties of novel 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates

Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac₂O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The ¹³C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG^‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol⁻¹ by the variable temperature ¹H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF₄⁻ and 12a-c·BF₄⁻) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF₄⁻) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF₄/Ac₂O afforded two kinds of novel products 11a-c·BF₄⁻ and 12a,c·BF₄⁻ in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF₄⁻ and 12a-c·BF₄⁻ observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF₄⁻ and 12a-c·BF₄⁻ were studied, and structural characterization of 11c·BF₄⁻ based on the X-ray crystal analysis and MO calculation was also performed.     

Naphthyridines. Part 3: First example of the polyfunctionally substituted 1,2,4-triazolo[1,5-g][1,6]naphthyridines ring system

Treatment of 1,2,4-triazoles (1) with diethylmalonate in bromobenzene gave 1,2,4-triazolo-[1,5-a]pyridines 2. Chlorination of 2 using POCl₃/DMF (Vilsmeier reagent) led to the isolation of 7-chloro-6-formyl-1,2,4-triazolo[1,5-a]pyridine derivative 4, which reacted with the stabilized ylid 5 to afford 6-ethoxycarbonylvinyl-1,2,4-triazolo[1,5-a]-pyridines 6. Azidation of 6 yielded the corresponding azido compound 7, (Scheme 2). Reduction of 7 with Na₂S₂O₄ gave the corresponding 7-amino compound 8, which cyclized in boiling DMF to give the novel 1,2,4-triazolo[1,5-g][1,6]naphthyridines 9. On the other hand, reacting 7 with one equivalent of PPh₃ (aza-Wittig reaction) in CH₂Cl₂ gave 7-imino-phosphorane derivative 10, and subsequent cyclization in boiling DMF afforded the new 1,2,4-triazolo[1,5-g][1,6]naphthyridine derivative 11 (Scheme 3). However, treatment of 10 with phenyl isothiocyanate in 1,2-dichlorobenzene at reflux temperature gave the new 1,2,4-triazolo[1,5-g][1,6]naphthyridine derivative 14 (Scheme 4). Refluxing 6 with excess of a primary amines 15a,b in absolute. EtOH yielded the corresponding 7-alkyl-amino-1,2,4-triazolo[1,5-a]pyridines 16a,b. These obtained amines 16a,b underwent intramolecular heterocyclization in boiling DMF to give the novel 9-alkyl-1,2,4-triazolo[1,5-g][1,6]-naphthyridines 17a,b, in excellent yields (Scheme 5).     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

Short-step syntheses and complexation properties of Z,Z-tribenzodidehydro- and all-Z-tribenzo[12]annulenes

Syntheses of all-Z-tribenzo[12]annulenes (1a-c) and Z,Z-tribenzodidehydro[12]annulenes (2a-c) by the reduction of the corresponding tribenzohexadehydro[12]annulenes 3a-c were carried out using a low valent titanium complex generated from Ti(O-i-Pr)₄ and i-PrMgCl. The unique structure of the first reduction products 2a-c as well as 1a-c was fully characterized. Complexation of these annulenes with silver(I) ions produces the corresponding silver complexes. Among them, the silver complexes of 2a-c exhibit interesting monomer-dimer equilibrium.     

The first methyl antimony linked dimeric tetrathiafulvalene and tetraselenafulvalenes

In quest of novel organic donors, dimeric tetrathiafulvalene (TTF) and tetraselenafulvalenes (TSFs) linked by a single or double methyl antimony bridge, MeSb(TTF)₂ (1), (MeSb)₂(TSF)₂ (cis-2 and trans-2), and MeSb(TSF)₂ (3), have been synthesized. Singly bridged 1 and 3 show three pairs of redox waves, whereas doubly bridged cis-2 and trans-2 show two pairs of redox waves similarly to TSF. The X-ray structural analyses of neutral crystals, 1, cis-2 and trans-2, have succeeded. In their structures, antimony and chalcogen atoms form close intermolecular contacts useful in constructing supramolecular networks.     

Synthesis and reactions of 3-alkylsulfanyl-1,3-dihydro-2,1-benzisothiazole 2,2-dioxides

Alkyl- and arylsulfanylation of 1,3-dihydro-2,1-benzisothiazole 2,2-dioxides (benzosultams) 1a-c and pyridosultam 1d with dialkyl and diaryl disulfides provides dithioacetals of 2-aminobenzaldehydes 6-13. 1,3-Dimethylbenzosultam 19 with disulfides forms 3-alkyl(aryl)sulfanyl-1,3-dimethylbenzosultams 20-22 that undergo thermal extrusion of SO₂ followed by a [1,5] sigmatropic hydrogen shift in the intermediate aza-ortho-xylylene leading to 1-arylvinyl sulfides 24-26. Tandem alkylation-sulfanylation of benzo- and pyridosultams 1a-d with 4-bromobutyl thiocyanate gives tetrahydrothiopyrano-spiro-benzosultams 27-30 that, after extrusion of SO₂ and [1,5] hydrogen shift, form 2-aryl-5,6-dihydro-4H-thiopyrans 32-35. Alkylation of pyridosultam 1d with 3-chloropropyl thiocyanate leads directly to 2-pyrido-3,4-dihydrothiophene derivative 37.     

Synthesis of new tetracyclic 7-oxo-pyrido[3,2,1-de]acridine derivatives

A series of (±)3-hydroxyl- and 2,3-dihydroxy-2,3-dihydro-7-oxopyrido[3,2,1-de]acridines were synthesized for antitumor evaluation. These agents can be considered as analogues of glyfoline or (±)1,2-dihydroxyacronycine derivatives. The key intermediates, 3,7-dioxopyrido[3,2,1-de]acridines (15a,b or 24a,b), for constructing the target compounds were synthesized either from 3-(N,N-diphenylamino)propionic acid (14a,b) by treating with Eaton’s reagent (P₂O₅/MsOH) (Method 1) or from (9-oxo-9H-acridin-10-yl)propionic acid (23a-c) via ring cyclization under the same reaction conditions (Method 2). Compounds 15a,b and 24a,b were converted into (±)3-hydroxy derivatives (25a-d), which were then further transformed into pyrido[3,2,1-de]acridin-7-one (28a-d) by treating with methanesulfonic anhydride in pyridine via dehydration. 1,2-Dihydroxylation of 28a-d afforded (±)cis-2,3-dihydroxy-7-oxopyrido[3,2,1-de]acridine (29a-d). Derivatives of (±)3-hydroxy (25a,b) and (±)cis-2,3-dihydroxy (29a-d) were further converted into their O-acetyl congeners 26a,b and 30a-d, respectively. We also synthesized 2,3-cyclic carbonate (31, 32, and 33) from 29a-c. The anti-proliferative study revealed that these agents exhibited low cytotoxicity in inhibiting human lymphoblastic leukemia CCRF-CEM cell growth in culture.     

Enantioselective epoxidation of α,β-unsaturated ketones catalyzed by stapled helical l-Leu-based peptides

Stapled helical l-leucine-based heptapeptides were synthesized and used as catalysts for the enantioselective epoxidation of α,β-unsaturated ketones. All N-terminal free stapled peptides were successfully used as chiral catalysts. Among them, the use of H-hS₃,₇hS-10 gave epoxide products with high enantioselectivities of up to 99% ee. Furthermore, the dominant conformations of the N-terminal protected stapled peptides R₃,₇R-10 and hS₃,₇hS-10 were investigated by ¹H NMR, IR, CD spectra, and X-ray crystallographic analysis. The peptide R₃,₇R-10 formed a right-handed (P) α-helix in solution and in the crystalline state, while hS₃,₇hS-10 formed a right-handed (P) 3₁₀-helix in solution.     

Salen-ligands based on a planar-chiral hydroxyferrocene moiety: Synthesis, coordination chemistry and use in asymmetric silylcyanation

Condensation of the O-protected hydroxyferrocene carbaldehyde (S_p)-1 with suitable diamines, followed by liberation of the hydroxyferrocene moiety leads to a new type of ferrocene-based salen ligands (3). While the use of ethylenediamine in the condensation reaction yields the planar-chiral ethylene-bridged ligand [(S_p,S_p)-3a], reaction with the enantiomers of trans-1,2-cyclohexylendiamine gives rise to the corresponding diastereomeric cyclohexylene-bridged systems [(S,S,S_p,S_p)-3b and (R,R,S_p,S_p)-3c], which feature a combination of a planar-chiral ferrocene unit with a centrochiral diamine backbone. Starting with the ferrocene-aldehyde derivative (R_p)-1, the enantiomeric ligand series (3d/e/f) is accessible via the same synthetic route.The (S_p)-series of these newly developed N₂O₂-type ligands was used for the construction of the corresponding mononuclear bis(isopropoxy)titanium (4a/b/c), methylaluminum (5a/b/c) and chloroaluminum-complexes (6a/b/c), which were isolated in good yields and identified by X-ray diffraction in several cases. The aluminum complexes (5/6) were successfully used in the Lewis-acid catalyzed addition of trimethylsilylcyanide to benzaldehyde, yielding the corresponding cyanohydrins in 45-62% enantiomeric excess.     

A one-pot, two step synthesis of 2,2-disubstituted 1-nitroalkenes

The reactions of ketones 1a-o, nitromethane 2, and a stoichiometric amount of piperidine 3a or ethylenediamine 3b in the presence of mercaptan 6a in THF or CH₃CN solution give high yields of β-nitrosulfides 7a-o. The latter can be oxidized by 8a (m-CPBA or m-CPBA/AcOH) at 0°C, 8b (H₂O₂/AcOH), or 8c (H₂O₂) at room temperature, thus generating β-nitroalkylsulfoxides 9a-o, which then undergo elimination to produce medium to high yields of 2,2-disubstituted-1-nitroalkenes 5a-o, when refluxed in a solution of ClCH₂CH₂Cl (1,2-dichloroethane). After preparation from 1a-o, 2, 3, and 6a, 7a-o were oxidized with 8a, 8b, or 8c in a mixture of CH₃CN and ClCH₂CH₂Cl to generate β-nitrosulfoxides 9a-o, which then underwent elimination under refluxing under one-pot conditions. Compounds 14 and 15g were also prepared using 13, 2, 3b, and 6, in a similar manner.     

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.     

Synthesis of sulfur containing analogues of the soluble guanylate cyclase inhibitor 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazin-1-one NS2028

Sulfur analogues of the soluble guanylate cyclase (sGC) inhibitor NS2028 1a are synthesized. Treating 8-bromo-2H-benzo[b][1,4]oxazin-3(4H)-one oxime (6) with 1,1′-thiocarbonyldiimidazole (1.1 equiv) gave the carbamothioate 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazine-1-thione (3a) in 83% yield. Alternatively reacting NS2028 1a with P₂S₅ (0.5 equiv) affords the carbamothioate 3a in 80% yield. Similar treatment of 8-aryl substituted NS2028 analogues 1b-d with P₂S₅ gave the carbamothioates 3b-d in 64-91% yields. Although quite stable, the carbamothioates 3a-d could be thermally isomerized in the presence of Cu (10 mol %) to afford the thiocarbamates 4a-d in high yields. Interestingly, in the case of carbamothioate 3a Pd and In metals also facilitated the isomerization. Furthermore, treatment of the thiocarbamates 4a-d with P₂S₅ (0.5 equiv) affords the carbamodithioates 5a-d in 72-89% yields. All new compounds are fully characterized including single crystal X-ray data for carbamothioate 3a and thiocarbamate 4a. Finally, a mechanism is proposed for the carbamothioate to thiocarbamate isomerization.     

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH₂CH₂CH₂P(OR′)₂]₂ (I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO)₂ (1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1-8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer,trans-(13a-20a) and mer,cis-[M(Me)(triphos)(CO)₂]I (13b-20b) (M = Ru, Fe; triphos = I-IV). The structures of 13a and 20a (as the tetraphenylborate salt (21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1-8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer,cis-[M(I)(triphos)(CO)₂]I (22-29) (M = Ru, Fe; triphos = I-IV) were produced. Complexes 22-29 could also be obtained by the addition of a stoichiometric amount of I₂ to 1-8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/b-20a/b with CO afforded the acetyl complexes mer,trans-[M(COMe)(triphos)(CO)₂]I, 30-37, respectively (M = Ru, Fe; triphos = I-IV). The ruthenium acetyl complexes 30-33 reacted slowly with 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34-37 were completed within 24-40 h to afford the corresponding zero valent complexes 5-8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer,trans-[Fe(COCD₃)(triphos)(CO)₂]I (38) and mer,trans-[Fe(¹³COMe)(triphos)(CO)₂]I (39).     

Bu3SnH-mediated 5-exo selective radical cyclization of N-vinyl-α,β-unsaturated amides leading to γ-lactams

Treatment of N-vinyl-α,β-unsaturated amides 1a-h with Bu₃SnH and a catalytic amount of AIBN in boiling benzene caused 5-exo cyclization of allylic O-stannyl ketyl radicals generated by addition of Bu₃Sn· on the amide-oxygen atoms to provide γ-lactams 2a-h after acidic workup. When enamide 1d was treated with Bu₃SnH in the presence of AIBN followed by aldehydes 3a-d, sequential radical cyclization and aldol reactions occurred to afford anti-adducts 4a-d and syn-adducts 5a,b.     

Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore

Polycarbohydrate macromonomers with different degrees of polymerization (DP), that is, end-functionalized (1 → 6)-2,5-anhydro-3,4-di-O-ethyl-d-glucitols with 4-ethynylbenzoyl groups (macromonomer 2: DP = 6.6, and macromonomer 3: DP = 9.5) were synthesized. The copolymerizations of these macromonomers and phenylactylene (PA) were carried out in various molar ratios to give poly(phenylacetylene)s bearing a polycarbohydrate ionophore as the graft chain with various grafting rates, poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y). These polymers showed split-type circular dichroism (CD) spectra in the long absorption region of the conjugated polymer backbones (280-500 nm). This indicated that poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y) had predominantly one-handed helical conformations in the backbones. The CD spectral patterns of these polymers were inverted in the presence of metal cationic guest molecules. On the other hand, control experiments using poly(phenylacetylene)s bearing a monocarbohydrate (poly-(4_x-co-PA_y)) and metal cations did not show such a CD spectral inversion. These results clearly indicated that the chiroptical switching of the poly(phenylacetylene)s bearing polycarbohydrate ionophore was attributable to the host-guest complexation of the polycarbohydrate ionophore with metal cations.     

4-Chloro-5-methyl-3-diphenylphosphino-1-phenyl-1,2,3,6-tetrahydrophosphinine as a bidentate P-ligand in a cis chelate Pt(II) complex

Double deoxygenation of a 3-phosphinoxido-1,2,3,6-tetrahydrophosphine oxide (2) led to bisphosphine 3-2 with an inverted ring P atom. The reaction of bidentate P-ligand 3-2 with dichlorodibenzonitrilo platinum(II) yielded the mixture of a novel cis chelate complex (7 = PtCl₂(3-2)) and a cis bis(3-diphenylphosphino-1,2,3,6-tetrahydrophosphininyl) complex (8 = PtCl₂(η¹-5)₂) containing two units of monodentate P-ligand 5.