Investigations on organoantimony compounds : X. Preparation of some heterocyclic chlorostibines

Some new heterocyclic chlorostibines have been prepared by treatment of the corresponding dimethyltin(IV) heterocycles with antimony trichloride.     

Syntheses, characterizations and crystal structures of new organoantimony(V) complexes with heterocyclic (S, N) ligand

Eight new organoantimony(V) complexes with 1-phenyl-1H-tetrazole-5-thiol [L¹H] and 2,5-dimercapto-4-phenyl-1,3,4-thiodiazole [L²H] of the type R_nSbL_5 − n (L = L¹: n = 4, R = n-Bu 1, Ph 2, n = 3, R = Me 3, Ph 4; L = L²: n = 4, R = n-Bu 5, Ph 6, n = 3, R = Me 7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental, FT-IR, ¹H and ¹³C NMR analyses. Among them complexes 2, 6 and 8 have also been confirmed by X-ray crystallography. The structure analyses show that the antimony atoms in complexes 2 and 6 display a trigonal bipyramid geometry, while it displays a distorted capped trigonal prism in complex 8 with two intramolecular Sb?N weak interactions. Furthermore, the supramolecular structure of 2 has been found to consist of one-dimensional linear molecular chain built up by intermolecular C-H?N weak hydrogen bonds, while a macrocyclic dimer has been found in complex 6 linked by intermolecular C-H?S weak hydrogen bonds with head-to-tail arrangement. Interestingly, one-dimensional helical chain is recognized in complex 8, which is connected by intermolecular C-H?S weak hydrogen bonds.     

Reactive fiber. V. Preparation and polymerization of p-styrenesulfonyl (β-chloroethyl)amide

p-Styrenesulfonyl(β-chloroethyl)amide (III) was prepared and copolymerized with styrene (M₁). The monomer reactivity ratios were determined (r₁ = 0.25 = 0.1, r₂ = 1.25 ± 0.25), and Q and e values were calculated (1.69 and 0.28, respectively). The polymer reacts with nucleophilic reagents such as amines and phenols in the presence of pyridine to the extent of 15–98%. Fibers from copolymers of acrylonitrile and III react with Congo Red in the presence of pyridine.     

Preparation of (S,S)‐Fmoc‐β2hIle‐OH, (S)‐Fmoc‐β2hMet‐OH,and (S)‐Fmoc‐β2hTyr(tBu)‐OH for Solid‐Phase Syntheses of β2‐ and β2/β3‐Peptides

The preparation of three new N‐Fmoc‐protected (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) β²‐homoamino acids with proteinogenic side chains (from Ile, Tyr, and Met) is described, the key step being a diastereoselective amidomethylation of the corresponding Ti‐enolates of 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones with CbzNHCH₂OMe/TiCl₄ (Cbz=(benzyloxy)carbonyl) in yields of 60–70% and with diastereoselectivities of >90%. Removal of the chiral auxiliary with LiOH or NaOH gives the N‐Cbz‐protected β‐amino acids, which were subjected to an N‐Cbz/N‐Fmoc (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) protective‐group exchange. The method is suitable for large‐scale preparation of Fmoc‐β²hXaa‐OH for solid‐phase syntheses of β‐peptides. The Fmoc‐amino acids and all compounds leading to them have been fully characterized by melting points, optical rotations, IR, ¹H‐ and ¹³C‐NMR, and mass spectra, as well as by elemental analyses.     

Preparation of α- or β-trifluoromethylated vinylstannanes and their cross-coupling reactions

α- or β-Trifluoromethylated vinylstannanes 1, 2a, 3 and 4 were prepared form 1,1-bis(phenylthio)-2,2,3,3,3-pentafluoropropylbenzene (5) via several steps. The cross-coupling arylation reactions of 1–4 with aryl iodides bearing a bromo, methoxy, methyl, nitro or trifluoromethyl group on para- or meta-position of benzene ring afforded the corresponding coupling products in good yields. Compounds 1, 2a and 4 underwent the acylation reaction with various types of acyl chlorides to give the corresponding trifluoromethylated enone derivatives in good yields. Reduction of trifluoromethylated enone derivatives with LiAlH₄, followed by Fridel-Craft’s type of cyclization with AlCl₃ provided trifluoromethylated indene derivatives in good yields.     

Synthesis of heterocyclic compounds VIII. 4H-Pyrans from α-benzoylcinnamonitriles

A new synthesis of substituted 4H-pyrans is reported. The base catalyzed reaction of substituted α-benzoy]cinnamonitri]es (I) with malononitrile yields 6-amino-2,4-diaryl-3,5-dieyano-4H-pyrans (III). Similarly, 6-amirio-2,4-diaryl-5-carbethoxy-3-cyano-4H-pyrans (IV) have been prepared Irom ethyl cyanoacetate.     

Studies on furan derivatives. II. Preparation of α-substituted β-2-(5-nitrofuryl)vinylamines

α-Subslituted β-2-(5-nitrofuryl)viriylamines were synthesized from α-ary]-β-2-(5-nitrofuryl)-aeryloyl azides and N-[α-substituled β-2-(5-nitrofuryl)vinyl] pyridinium bromides.     

Tautomeric equilibrium of ketonic and cis- and trans-enolic forms of β-dicarbonyl compounds in solution

In this paper the tautomeric equilibrium of ketonic and cis- and trans-enolic forms of β-dicarbonyl compounds is considered as an acid-base protolytic one. The application of the Brønsted-Izmaylov theory has enabled to suggest a general equation K_TS = for keto-enol equilibrium constant, depending on the solvent, the well known Meyer's equation being included in it as a particular case. Equilibrium constants have been bromometrically determined in a number of solvents of keto-enols of three types, i.e. “cis-fixed”, “trans-fixed” and that involving both stereo-isomeric forms. A method for quantitative determination of cis-trans-enol equilibrium had been proposed.     

The structure–activity relationship of some hexacoordinated dimethyltin(IV) complexes of fluorinated β‐diketone/β‐diketones and sterically congested heterocyclic β‐diketones

The study was focused on the structure–activity relationship of some newly synthesized hexacoordinated dimethyltin(IV) complexes of fluorinated β‐diketone/β‐diketones and sterically congested heterocyclic β‐diketones. These complexes were screened for their antibacterial activity against a Gram‐negative bacterium (Pseudomonas aeruginosa) and Gram‐positive bacteria (Streptomyces griseus, Staphylococcus aureus, Bacillus subtilis) and the results were compared with those of a standard antibacterial drug. Some of the complexes were also screened for their antifungal activity against various fungi (Aspergillus niger, A. flavus, Trichoderma viride, Fusarium oxysporum) and were found to be active. These new hexacoordinated complexes of dimethyltin(IV) were generated by reactions of dimethyltin(IV) dichloride and sodium salts of fluorinated β‐diketone/β‐diketones and sterically congested heterocyclic β‐diketones in 1:1:1 molar ratio in refluxing dry benzene. Plausible structures of these complexes were suggested with the aid of physicochemical and spectroscopic studies. ¹¹⁹Sn NMR spectral data revealed the presence of a hexacoordinated tin centre in these dimethyltin(IV) complexes. Copyright © 2015 John Wiley & Sons, Ltd.     

Tandem epoxysilane rearrangement/Wittig-type reactions using γ-phosphinoyl- and γ-phosphonio-α,β-epoxysilane

Reaction of γ-phosphinoyl- and γ-phosphonio-α,β-epoxysilane with a base followed by addition of a ketone or an aldehyde afforded dienol silyl ether derivatives via a tandem process that involves base-induced ring opening of the epoxide, Brook rearrangement, and Wittig-type reaction.     

Discotic metallomesogens: Synthesis and properties of square planar metal bis(β-diketonate) complexes

Discotic β-diketonate liquid crystals containing palladium(II), and oxovanadium(IV), (V≡0), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), have been prepared and characterized. These are the first enantiotropic discotics containing Pd(II) and among the earliest examples containing VO(IV). The best-behaved Pd(II) complex is [Pd(DK 10, 10)₂], and it also is probable that the complexes [Pd(DKn,n)₂] (n = 7-9) are mesomorphic, however their characterization is difficult due to decomposition in the isotropic phase. The mesophase of [Pd(DK 10²,10²)₂], which appears below 100°C, is suggested to be an example of the rare N_d phase on the basis of optical microscopy. The complex [VO(DK8,8)₂] is an enantiotropic discotic vanadyl complex; the monotropic behaviour of [VO(DK 10,10)₂] was also confirmed. It is suggested that the discotic phase which occurs for [VO(DK 8,8)₂] is more organized than that of [Cu(DK 8,8)₂].     

Preparation of β2‐Amino Acid Derivatives (β2hThr, β2hTrp, β2hMet, β2hPro, β2hLys,Pyrrolidine‐3‐carboxylic Acid) by Using DIOZ as Chiral Auxiliary

The title compounds were prepared from valine‐derived N‐acylated oxazolidin‐2‐ones, 1 – 3, 7, 9 , by highly diastereoselective (≥ 90%) Mannich reaction (→ 4 – 6 ; Scheme 1) or aldol addition (→ 8 and 10 ; Scheme 2) of the corresponding Ti‐ or B‐enolates as the key step. The superiority of the ‘5,5‐diphenyl‐4‐isopropyl‐1,3‐oxazolidin‐2‐one’ (DIOZ) was demonstrated, once more, in these reactions and in subsequent transformations leading to various t‐Bu‐, Boc‐, Fmoc‐, and Cbz‐protected β²‐homoamino acid derivatives 11 – 23 (Schemes 3–6). The use of ω‐bromo‐acyl‐oxazolidinones 1 – 3 as starting materials turned out to open access to a variety of enantiomerically pure trifunctional and cyclic carboxylic‐acid derivatives.     

Solvent‐free reactions of alcohols with β‐dicarbonyl compounds catalyzed by iron(III) chloride

The direct substitution of alcohols and β‐dicarbonyl compounds was catalyzed with FeCl₃ under solvent‐free conditions. The catalyst loading could be decreased to 0.01 mol% at high activities. It was shown that the reaction proceeded in two steps via the etherification of the alcohols. This method provided an easy and practical procedure for C? C bond formation.Copyright © 2007 John Wiley & Sons, Ltd.