PubMed Health⌕ Search

Biomedical subjects

Robert E Mulvey

Publications and source records attributed to Robert E Mulvey.

At least 19 recordsLinked to original sources
PubMed2006

New reactivity and structural insights of alkali-metal-mediated alumination in directed ortho-alumination of a tertiary aromatic amide.

The first reported sodium alkyl(TMP)aluminate reagent to be synthesised and crystallographically characterised, [TMEDA.Na(mu-TMP)(mu-(I)Bu)Al((I)Bu)2], reacts as an amido base towards phenylacetylene to form crystalline [(TMEDA)2.Na(mu-CCPh)(mu-(I)Bu)Al((I)Bu)2]; whereas the congeneric TMEDA-stabilised lithium (TMP)aluminate exhibits dual alkyl/amido basicity in its reaction with N,N-diisopropylbenzamide to form a novel heterobimetallic-heterotrianionic crystalline complex [{PhC(=O)N(iPr)2}.Li{2-[1-C(=O)N(iPr)2]C6H4}{Me2NCH2CH2N(Me)CH2}Al(iBu)2], which, in addition to having an ortho-deprotonated benzamide ligand, also contains a methyl-deprotonated TMEDA ligand and a neutral benzamide molecule ligated to lithium.

Journal Article↗
PubMed2006

Alkali-metal-mediated zincation of anisole: synthesis and structures of three instructive ortho-zincated complexes.

The new concept of alkali-metal-mediated zincation (AMMZ), formally a zinc-hydrogen exchange reaction but one that requires the participation of an alkali metal, is applied here to the alkyl aryl ether anisole, an important molecule for studying directed ortho-metalation (DoM) chemistry. Treating one molar equivalent of anisole with the lithium dialkyl-TMP zincate reagent [THF.Li(mu-TMP)(mu-tBu)Zn(tBu)] (1) in hexane solution affords the mono-ortho-zincated complex [THF.Li(mu-TMP)(mu-o-C6H4OMe)Zn(tBu)] (2), which establishes that 1 functions as an alkyl base although previously it was regarded as an amido (TMP) base in other DoM applications. Treating two molar equivalents of anisole with 1, and increasing the reaction time, affords the bis-ortho-zincated complex [THF.Li(mu-TMP)(mu-o-C6H4OMe)Zn(o-C6H4OMe)] (3), which establishes that 1 can also function as a dual alkyl base. Omitting THF and rerunning the reaction with one or two molar equivalents of anisole affords [Ph(Me)O.Li(mu-TMP)(mu-o-C6H4OMe)Zn(tBu)] (4), which remarkably contains a combination of neutral and ortho-deprotonated anisole ligands. On isolating crystalline 4 from solution and adding THF, it converts to 2 and then to 3 on further stirring of the solution, as determined by NMR studies. This fact, along with other observations, would suggest that a complex-induced proximity effect does not need to be invoked to explain the observed zincation of anisole. The crystal structures of 2-4 are presented, as are their 1H, 13C, and 7Li NMR spectra recorded in C6D6 solution.

Journal Article↗
PubMed2006

Building an extended inverse crown motif via alkali-metal-mediated alpha-magnesiation of furan.

deprotonated selectively at the -position by the mixed-metal alkyl-amido base [(TMEDA) x Na(Bun)(TMP)Mg(TMP)] to generate a transient intermediate which undergoes disproportionation to the disodium dimagnesium hexafuryl tri(thf) complex [{{(thf)3 x Na2}{(TMEDA) x Mg2}(2-C4H3O)6}infinity], a new type of inverse crown structure with triply-stabilized (through Mg-C , Na-O and Na...C-C interactions) furyl guest anions, and the tris(amide) [(TMEDA)x.NaMg(TMP)3].

Journal Article↗
PubMed2005

Trapping, stabilization, and characterization of an enolate anion of a 1,6-adduct of benzophenone chelated by a sodium alkylamidozincate cation.

There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR'2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA.Na(mu-tBu)(mu-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2C=O), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic study of the adduct reveals a molecular structure based on a near-planar, four-element (NaOZnN) ring with a TMP-N and an enolato-O bridge. The Na and Zn atoms also carry terminal TMEDA (N,N'-attached) and tBu (C-attached) ligands, respectively. Also included are 1H/13C NMR spectroscopic data for the adduct when dissolved in cyclohexane-d12 solution.

Anions↗
PubMed2005

A mixed iron(III)/lithium alkoxide.

The heterometallic alkoxide catena-poly[[tetra-mu2-tert-butoxo-1:2kappa4O:O;1:3kappa4O:O-bis(tetrahydrofuran)-2kappaO,3kappaO-iron(III)dilithium(I)]-mu-bromo], [FeLi2Br(C4H9O)4(C4H8O)2]n, forms a one-dimensional chain through an a-glide. This conformation is achieved through the formation of Fe(III)/O/Li/O rings and Li-Br-Li bridges.

Journal Article↗
PubMed2005

Sodium dialkyl-amidozincates: alkyl or amido bases? An experimental and theoretical case study.

Alkali metal zincate reagents are attracting considerable attention at present in respect to their often special reactivity/selectivity in hydrogen-metal and halogen-metal interconversion reactions. Heteroleptic diorgano-amidozincates, typified by lithium di-tert-butyltetramethylpiperidinozincate, have proved to be especially useful reagents in such applications. In this paper the related sodium TMP-zincate, prepared as its TMEDA (N,N,N',N'-tetramethylethylenediamine) adduct, [TMEDA.Na(mu-tBu)(mu-TMP)Zn(tBu)], 1, is introduced. This new zincate was synthesized from a 1:1:1 mixture of tBu2Zn, NaTMP, and TMEDA in hexane solution, as a colorless crystalline solid in an isolated yield of 58%. It has been characterized in solution by 1H and 13C NMR spectroscopic studies. An X-ray crystallographic study reveals that 1 adopts a five-membered (NaNZnCC) ring system featuring a TMP bridge and an unusual, asymmetrical tBu bridge involving a Na...Me agostic contact. Probing the basicity of 1, reaction with benzene affords the new hetero(tri)leptic zincate [TMEDA.Na(mu-Ph)(mu-TMP)Zn(tBu)], 2, which has also been crystallographically characterized. Thus, in this hydrogen-metal exchange reaction 1 functions as an alkyl base, with the elimination of butane, as opposed to an amido base. Also reported are DFT calculations using B3LYP functionals and the 6-311G** basis set on model zincate systems, which intimate that the preference of 1 for tBu ligand transfer over TMP ligand transfer in the reaction toward benzene is due to favorable thermodynamic factors.

Journal Article↗
PubMed2005

Synthesis and characterisation of a series of alkylmagnesium amide and related oxygen-contaminated "alkoxy" compounds.

Synthesised either by an unusual tert-butyl metathesis between tert-butyllithium and a n,s-butylmagnesium amide or by reaction of an alkyl Grignard reagent and a sodium amide, five tert-butylmagnesium amides, Bu(t)MgDBA (5)(DBA=dibenzylamide), Bu(t)MgDA (6)(DA=diisopropylamide), Bu(t)MgHMDS (7)(HMDS=1,1,1,3,3,3-hexamethyldisilazide), Bu(t)MgTMP (8)(TMP=2,2,6,6-tetramethylpiperidide) and Bu(t)MgNCy2 (9)(cy=cyclohexyl) have been isolated as crystalline solids. All five amides have been characterised by X-ray crystallography and solution NMR spectroscopic studies. The former studies reveal a common dimeric molecular structure with amido bridges in a planar (MgN)2 ring and terminal Bu(t) ligands on the Mg atoms. Also described is the dodecameric primary amide [Bu(n)MgN(H)Dipp]12 (10a) and its monomeric solvate Bu(n)MgN(H)Dipp.TMEDA (10b)(Dipp=2,6-diisopropylphenyl; TMEDA=N,N,N',N'-tetramethylethylenediamine). The crystal structures of the oxo-insertion products Bu(t)MgOBu(t).THF (11), Bu(t)Mg(mu-OBu(t))(mu-TMP)MgTMP (12) and Mg(OBu(n))HMDS.solv [solv=THF (13a) or Et2O (13b)], made fortuitously during the course of this work, are also presented.

Journal Article↗
PubMed2004

Crystallographic characterisation of binary alkali metal alkoxide-magnesium bis(alkyl) mixtures: differential binding of Na+ and K+ to a common dinuclear diorganomagnesiate.

Relevant to mixtures studied in solution and utilised in styrene polymerisation but hitherto not characterised in the solid, two crystal structures of alkali metal alkoxide-magnesium bis(alkyl) co-complexes have been determined, revealing that in binding to the C2O tripodal face of a common organomagnesiate anion, Na+ prefers O-coordination, whereas K+ prefers C-coordination.

Journal Article↗