Terminal Ethynyl Groups Research Articles

Synthesis of new ethynylene‐containing aromatic polyamides by palladium‐catalyzed polycondensation of aromatic amide monomers having terminal ethynyl and halogen groups

Polyamide [C≡CPhNHCOPh] n was obtained by polycondensation of monomers XPhNHCOPhY (X= m-Br, p-Br, m-CH≡C; Y= p-CH≡C, p-Br, p-I, m-I). The polymer was soluble in various organic solvents (NMP, DMAc , DMF, m-cresol) and had 10% weight loss temperature of 530°C under nitrogen. DSC curve showed that crosslinking of the ethynylene groups occurred at 270°C

Synthesis of Some Polyacetylenes

Abstract Twenty seven polyacetylenes having an aryl group in the chain have been synthesized using silylation as the protection of the terminal ethynyl group followed by oxidative coupling of the acetylenes and Cadiot-Chodkiewicz coupling reactions. The compounds have been characterized by their IR, NMR, UV and Mass spectral data.

Some new dienophiles in the diels-alder reaction with active cyclic dienes

A comparative study of the Diels-Alder reaction have been carried out for three types of cyclic dienes: cyclopentadiene (CPD), hexachlorocyclopentadiene (HCP), and tetrachloro-1,2-benzoquinone (TCBQ) with dienophiles of five types: monosubstituted acetylenes (propargyl alcohol and its esters), conjugated amines (allyl acetylene, allyl ethynyldimethylcarbonol and its esters), conjugated dienes (2-methylhexadiene-3,5-ol-2 and its esters, 1-ethoxy- and 1-ethoxycarbonylbutadiene-1,3), and conjugated trienes (hexatriene-1,3,5 and 5-methylhexatriene-1,3,5). It was found that conjugated trienes react with dienes of all types under mild conditions and give only the monoadducts through the terminal vinyl or ethynyl group.

Ethynyl‐terminated polyarylates: Synthesis and characterization

AbstractHydroxy‐terminated polyarylates (HTPA) with number‐average molecular weights of approximately 2500, 5000, 7500, and 10,000 were synthesized and converted to corresponding 4‐ethynylbenzolyloxy‐terminated polyarylates (ETPA) by reaction with 4‐ethynylbenzoyl chloride. The terminal ethynyl groups were thermally reacted to provide chain extension and crosslinking. The cured ETPA exhibited higher glass transition temperatures (Tg) and better solvent resistance than a high molecular weight linear polyarylate. Solvent resistance was further improved by curing 2,2‐bis(4‐ethynylbenzoyloxy‐4′‐phenyl) propane, a coreactant, with ETPA at concentrations of approximately 10% (w/w).

Laurencia natural products. Part I. Crystal structure and absolute stereochemistry of laurencin

The crystal structure and the absolute stereochemistry of laurencin have been determined by a single-crystal X-ray analysis. The crystals are orthorhombic, space group P212121 with four molecules of C17H23O3Br in a unit cell of dimensions a= 7·70, b= 9·70, c= 22·93 A. The structure was solved by the heavy-atom method and refined by least-squares calculations. R is 0·103 for 1152 reflexions. The absolute stereochemistry was determined by consideration of anomalous dispersion effects. The molecule is unusual in that it has an eight-membered ether-ring containing a cis-double bond. Laurencin provides an example of strong intermolecular–C⋮CH ⋯ O hydrogen-bonding in the solid state as revealed by i.r. absorption data. In the crystal, the terminal ethynyl group of a trans-hex-3-ene-5-yne side-chain is involved in a bifurcated hydrogen bond with ether and acetate oxygen atoms of a neighbouring molecule.

Synthesis of aryl and heterocyclic acetylenes via copper acetylides

Ethynylbenzene (I), 1-ethynylnaphthalene (IX), 2-ethynylthiophen (IV), and 2-ethynyl-5-iodothiophen (XII) have been prepared from the corresponding iodo-derivatives (V), (VII), (II), and (X), by reaction with copper(I) 3,3-diethoxyprop-1-ynide to give αβ-acetylenic aldehydes, followed by base-catalysed deformylation. Alternatively, copper(I) 3-tetrahydropyranyloxy-prop-1-ynide gave the αβ-acetylenic alcohols (XVIII), (XIX), (XIII), (XX), and (XV), which were oxidised with nickel peroxide and then deformylated, or oxidised in aqueous alkali directly, to the same acetylenes (I), (IX), (IV), (XII), and 5-ethynyl-2,2′-bithienyl (XVII). The application of this sequence to the protection of terminal ethynyl groups is indicated.

The protection of terminal ethynyl groups in the oxidative couplings of acetylenes

The protection of terminal ethynyl groups in the oxidative couplings of acetylenes

The protection of terminal ethynyl groups in Grignard syntheses

The trimethylsilyl group can be used to protect a terminal ethynyl group in Grignard syntheses. For example, a Grignard reagent can be made in tetrahydrofuran from the easily prepared compound (p-bromophenylethynyl)-trimethylsilane, and carbonation gives the acid (p-carboxyphenylethynyl)trimethylsilane, which on treatment with dilute alkali gives p-ethynylbenzoic acid in 55% overall yield. The corresponding meta-acid can be made analogously.This method of protection has been used in the preparation of the compounds m- and p-HCC·C6H4·MR3, where MR3= SiMe3, SiEt3, or SnMe3.

Synthesis of aryl and heterocyclic acetylenes via copper acetylides

Ethynylbenzene (I), 1-ethynylnaphthalene (IX), 2-ethynylthiophen (IV), and 2-ethynyl-5-iodothiophen (XII) have been prepared from the corresponding iodo-derivatives (V), (VII), (II), and (X), by reaction with copper(I) 3,3-diethoxyprop-1-ynide to give αβ-acetylenic aldehydes, followed by base-catalysed deformylation. Alternatively, copper(I) 3-tetrahydropyranyloxy-prop-1-ynide gave the αβ-acetylenic alcohols (XVIII), (XIX), (XIII), (XX), and (XV), which were oxidised with nickel peroxide and then deformylated, or oxidised in aqueous alkali directly, to the same acetylenes (I), (IX), (IV), (XII), and 5-ethynyl-2,2′-bithienyl (XVII). The application of this sequence to the protection of terminal ethynyl groups is indicated.