Peter N. Preston

Synthesis of 1,3-Diynes in the Purine, Pyrimidine, 1,3,5-Triazine and Acridine Series

Abstract A range of conjugated 1,3-diynes, R1CCCCR2, has been prepared that incorporate the following heteroaromatic units as head groups of the substituents R1 and/or R2: pyrimidinyl, purinyl, 2,4-diamino-1,3,5-triazinyl and acridinyl. Compounds containing the first three groups as terminal heterocyclic substituents in both R1 and R2 are bonded through methylene linkers {(CH2)n, n=1, 4 or 9} to the 1,3-diyne; also reported are amphiphilic species with R2=n-C10H21 and a single heteroaromatic head group in chain R1. Compounds in the acridine series are also amphiphiles and contain quaternised 1′-(9-acridinylamino)- and 1′-(6-chloro-2-methoxyacridinylamino)- terminal substituents linked by PEG and methylene units to the diyne function. The new diynes have been synthesised by oxidative coupling of the corresponding ω-heteroaromatic functionalised 1-alkyne or by transformation of terminal groups on preformed diynes.

Synthesis and reactivity of benzylic sulfonium salts: benzylation of phenol and thiophenol under near-neutral conditions

Abstract A series of benzyldimethylsulfonium - and related hydrogensulfate salts have been synthesized from the ternary system ArCH 2 OH:H 2 SO 4 : Me 2 S or tetrahydrothiophene. The salts are generally stable crystalline solids, but anomalously high reactivity is observed for 9-(anthrylmethyl)dimethylsulfonium hydrogensulfate. Selected sulfonium salts have been used for the O - and S -benzylation of phenol and thiophenol, respectively, in a two phase system under near-neutral conditions. The benzylation of oximes and benzimidazole under basic conditions is also described.

Synthesis and characterization of cobalt and molybdenum complexes derived from linear conjugated diynenes, triynedienes and tetraynetrienes

Abstract Z -1,6-Bis(trimethylsilyl)hexa-1,5-diyn-3-ene ( 2a ), E -hexa-1,5-diyn-3-ene ( 3b ) and related compounds ( 3a , c and d ) were synthesized by standard methods. The Grignard reagent ( 3e ) derived from 1-phenylhexa-1,5-diyn-3-ene ( 3d ) was coupled with E -1-chloro-4-phenyl-1-buten-3-yne to give E , E -1,10-diphenyldeca-1,5,9-triync-3,7-diene ( 4 ) and with E -1,2-dichloroethene to give E , E , E -1,14-diphen-yltetradeca-1,5,9,13-tetrayne-3,7,11-triene ( 5 ). Hexa-1,5-diyn-3-ene complexes coordinated to one ( 7a , 8 ) and two ( 6a-d ) hexacarbonyldicobalt units were prepared from the appropriate ligands and octacarbonyldicobalt. Tris- ( 9 ) and tetrakis- ( 10 ) hexacarbonyldicobalt complexes of the triynediene ( 4 ) and tetraynetriene ( 5 ) ligands were prepared similarly. Mono ( 7b ) and bis ( 6e ) di-η 5 -cyclopentadienyltetra-carbonyldimolybdenum complexes of E -1,6-bis(trimethylsilyl)hexa-1,5-diyn-3-ene were prepared by treating free diynene ( 3a ) with the appropriate amount of [(η 5 -C 5 H 5 )Mo(CO) 2 ] 2 . Spectroscopic characteristics (NMR, IR, UV) of the complexes are presented and discussed.

Thermal and photochemical reactions of η5-cyclopentadienyl(naphthoyl)(dicarbonyl)iron complexes with alkynes: formation of benzindenones and dihydropentalenones

η5-Cyclopentadienyl(1- and 2-naphthoyl)(dicarbonyl)iron complexes (6a) and (6b) have been synthesised from the appropriate acid chlorides and sodium η5-cyclopentadienyl(dicarbonyl)iron-(1–). UV irradiation of (6a) and (6b) separately with diphenylacetylene in benzene gives 1,2-diphenyl-3H-benz[e]inden-3-one (8), and 2,3-diphenyl-1H-benz[e]inden-1-one (7) respectively, together with smaller quantities of bis(η5-cyclopentadienyl)(tetracarbonyl)di-iron. The benz[e]indenones (7) and (8) are also formed in low yield from diphenylacetylene and η5-cyclopentadienyl(1- and 2-naphthoyl)(dicarbonyl)iron complexes respectively, in hot decalin. A second product from the thermal reaction is c-4,c-6a-dihydro-4-(1- or 2-naphthyl)-2,3-diphenylpentalen-1(r-3aH)-one (9a) or (9b), respectively, incorporating a cyclopentadienyl group. A compound of the last type (9c) is also formed in a thermal reaction of η5-cyclopentadienyl(1-naphthoyl)(dicarbonyl)iron with 1-phenylpropyne. The molecular structures of (7) and (9a) were elucidated by X-ray crystallography.

Synthesis of pyrido-1,2,4-thiadiazines related to antihypertensive 1,2,4-benzothiadiazine-1,1-dioxides

Abstract Oxidation of 3-phenyl-2 H -pyrido[2,3- e ]-1,2,4-thiadiazine with sodium hypochlorite and, separately, m -chloroperoxybenzoic acid afforded a 1,1-dioxide and a 5-oxide derivative, respectively. Further examples of such 1,1-dioxide derivatives were synthesised by treating 2-amino-5-methylpyridine with orthoesters and these were subsequently oxidised to novel 1 , 1,5-trioxides. A short route has been developed for the synthesis of 4-aminopyridine-3-sulfonamide which was used for the preparation of 4 H -pyrido[4,3- e ]-1,2,4-thiadiazine 1,1-dioxides; oxidation of the parent member of the series gave a 1,1,7-trioxide derivative. 3-Aminopyridine-4-sulfonamide has been prepared, and then condensed with triethyl orthoformate to afford 4 H -pyrido[3,4- e ]-1,2,4-thiadiazine 1,1-dioxide.

Synthesis, characterisation and optical properties of metal-containing polydiacetylenes

Soluble polydiacetylenes (CR–CC–CR′)n[R = R′=(CH2)9O2CCH2Ph (2a); R =(CH2)9CH3, R′=(CH2)8CO2CH2Ph (2b)] have been synthesized and reacted with Co2(CO)8 to introduce varying proportions of Co2(CO)6 groups, attached as Co2C2 tetrahedrane units, at the alkyne bonds of the conjugated ene–yne backbone. These metallated polymers have been characterised by analytical data and by IR, 13C[1H] NMR and UV–VIS spectroscopy. Reactions between polydiacetylenes 2a or 2b and [M2(CO)4(η5-C5H5)2](M = Mo, W) are also reported. The presence of fast optical non-linearities in these soluble polymeric materials was confirmed by fluorescence lifetime measurements and optical characterisation of the imaginary part of χ(3) These studies were conducted on a picosecond timescale to allow electronic contributions to be resolved, and the related lm χ(3) values tabulated against metal content and solution concentration.

Preparation, structural studies, and some reactions of new heterobinuclear complexes containing molybdenum, tungsten, or manganese and rhodium or copper; X-ray crystal structures of [MoRh(CO)(µ-CO)2(PPh3)2(η-C5H5)] and two isomers of [CuW(CO)3(PPh3)2(η-C5H5)]

Reaction of the anions [M(CO)3(η-C5H5)]– or [Mn(CO)5]– with [RhCl(PPh3)3] in tetrahydrofuran produces the formally unsaturated bimetallic complexes [MRh(CO)(µ-CO)2(PPh3)2(η-C5H5)][M = Mo (1) or W (2)] or [MnRh(CO)2(µ-CO)2(PPh3)3](3) respectively. An X-ray diffraction study of (1) has established its molecular structure: monoclinic, space group P21/c, a= 18.102(2), b= 10.407(1), c= 20.736(2)A, β= 104.99(1)°, and Z= 4. The structure, determined from 5 233 independent intensities, was refined to R= 0.036 (R1= 0.074). It comprises a Mo(CO)(η-C5H5) group bonded to Rh(PPh3)2 with a short Mo–Rh separation 2.588(1)A and two asymmetric (µ-CO) ligands with Mo–C 1.980(6) and 2.026(5)A and Rh–C 2.182(6) and 2.092(5)A; the Mo(µ-CO)2Rh framework has a dihedral angle (Mo–Rh–C/Mo–Rh–C) of 161°. I.r., 1H and 31P-{1H} n.m.r. spectra of complexes (1)–(3) are presented and discussed in relation to their structures: formal metal–metal multiple bonds, Rh[grahpic omitted]M, are proposed. Complex (1) acts as a catalyst in hydrogenation of cyclohexene and reactions involving the cleavage of M–Rh bonds are described for complexes (1) and (3). Reactions of [M(CO)3(η-C5H5)]– with [{CuCl(PPh3)}4] give the bimetallic products [CuM(CO)3-(PPh3)2(η-C5H5)][M = Mo (4) or W (5)] in relatively low yields. Complex (5) has been obtained in two isomeric crystalline forms, (5a) and (5b), for which X-ray crystal structure determinations have been undertaken: (5a), triclinic, space group P(no. 2), a= 12.404(4), b= 11.756(3), c= 14.208(3)A, α= 101.4(2), β= 79.5(2), γ= 110.3(2)°, and Z= 2; (5b), monoclinic, space group P21/c(no. 14), a= 17.991 (3), b= 10.098(2), c= 21.608(2)A, β= 105.66(1)°, with Z= 4. The structures of (5a) and (5b) have been refined to residuals R= 0.058 and 0.034 from 3 997 and 4 009 unique reflections, respectively. Both isomers contain W(CO)3(η-C5H5) groups bonded to Cu(PPh3)2 units. The carbonyl ligands are essentially terminally bound to W but two CO groups show some semibridging interactions with Cu, especially in structure (5b); Cu–C 2.309(13) and 2.405(13)A in (5a), 2.260(8) and 2.197(9)A in (5b). In (5a) the Cu(PPh3)2 unit occupies the position typical of a ligand to W in a complex with ‘four-legged piano stool’ geometry [W–Cu 2.721(1)A; dihedral angle (W–Cu–C/W–Cu–C′) 139.8°]. In (5b) the W(µ-CO)2Cu fragment is almost planar (W–Cu–C/W–Cu–C′ 170.9°) and W–Cu [2.771 (1)A] is longer. The structures and bonding of complexes (4) and (5) are discussed in relation to i.r. and n.m.r. spectral data; in solution,13C-{1H} n.m.r. spectra support a non-rigid structure for complex (5).

Polymerization of benzyl alcohol in anhydrous hydrogen fluoride : an efficient synthesis of poly(phenylenemethylene)

Abstract It has been shown that benzyl alcohol is transformed rapidly and almost quantitatively into poly(phenylenemethylene) by adding it to anhydrous hydrogen fluoride at 16°C; the product is the so-called ‘soluble poly(phenylenemethylene)’ with a degree of polymerization of ≈20. p -Methylbenzyl alcohol has also been oligomerized by a similar procedure. The potential for adaption to industrial-scale use is highlighted.

Investigation of the Curing Mechanism in PMR Polyimide Resin

Investigation of the curing mechanism of PMR-15 has revealed detailed information regarding reaction pathways and physical. transitions involved during imidization and cross-linking. The oligomeric intermediates formed during staging contain a distribution of different molar mass species of diverse chemical nature, the relative amounts of which vary according to conditions of stoichiometry, temperature, etc. adopted. The cross-linking temperature profile of the oligomers, and physical transitions and further cross-linking/degradative behaviour of the polyimide resin have been eludated via DMTA.

Co-ordinatively unsaturated alkyne complexes of molybdenum and tungsten. Reactions of [MCl(CF3CCCF3)2(η-C5H5)](M = Mo or W) with heterocyclic thiolates leading to η2-vinyl complexes

Reactions of Tl(SR)(SR–= pyridine-2-thiolate, pyrimidine-2-thiolate, or thiazoline-2-thiolate) with the bis(hexafluorobut-2-yne) complex [MoCl(CF3CCCF3)2(η-C5H5)] give products [[graphic omitted]}(CF3C-CCF3)(η-C5H5)] containing a novel η2-vinyl ligand resulting from nucleophilic attack of nitrogen on a co-ordinated alkyne. The same pyridine-2-thiolate complex is obtained from the reaction of [MoCl(CF3CCCF3)2(η-C5H5)] with the thallium(I) salt of 2-mercaptopyridine N-oxide, in addition to [[graphic omitted]}(η-C5H5)]. The complex [WCl(CF3CCCF3)2(η-C5H5)] reacts with thallium(I) pyridine-2-thiolate to give the η2-vinyl complex [[graphic omitted]}(CF3CCCF3)(η-C5H5)], whereas with Tl(SC5H4NO) cyclopentadienyl-ligand displacement is also observed giving the co-ordinatively unsaturated bis(hexafluorobut-2-yne) complexes [W(SC5H4NO)2(CF3CCCF3)2] and [W(SC5H4N)(SC5H4NO)(CF3CCCF3)2]