Andrew E. H. Wheatley

Mixed alkylamido aluminate as a kinetically controlled base.

The mechanisms by which directed ortho metalation (DoM) and postmetalation processes occur when aromatic compounds are treated with mixed alkylamido aluminate i-Bu3Al(TMP)Li (TMP-aluminate 1; TMP = 2,2,6,6-tetramethylpiperidide) have been investigated by computation and X-ray diffraction. Sequential reaction of ArC(=O)N(i-Pr)2 (Ar = phenyl, 1-naphthyl) with t-BuLi and i-Bu3Al in tetrahydrofuran affords [2-(i-Bu3Al)C(m)H(n)C(=O)N(i-Pr)2]Li x 3 THF (m = 6, n = 4, 7; m = 10, n = 6, 8). These data advance the structural evidence for ortho-aluminated functionalized aromatics and represent model intermediates in DoM chemistry. Both 7 and 8 are found to resist reaction with HTMP, suggesting that ortho-aluminated aromatics are incapable of exhibiting stepwise deprotonative reactivity of the type recently shown to pertain to the related field of ortho zincation chemistry. Density functional theory calculations corroborate this view and reveal the existence of substantial kinetic barriers both to one-step alkyl exchange and to amido-alkyl exchange after an initial amido deprotonation reaction by aluminate bases. Rationalization of this dichotomy comes from an evaluation of the inherent Lewis acidities of the Al and Zn centers. As a representative synthetic application of this high kinetic reactivity of the TMP-aluminate, the highly regioselective deprotonative functionalization of unsymmetrical ketones both under mild conditions and at elevated temperatures is also presented.

The first molecular main group metal species containing interstitial hydride

Lithium cages containing hydride: The reaction of tBuLi with Me(2)AlN(2-Pyr)Ph in toluene gave [Li(8)(H){N(2-Pyr)Ph}(6)](+)[Li(Me(2)AltBu(2))(2)](-), whose cation is the first molecular main group metal species to contain interstitial hydride (the cluster core is shown in the picture). Treatment of the reaction mixture with THF gave the neutral hydride Li(7)(H)[N(2-Pyr)Ph](6), which has a capped octahedral (Li(+))(7) cluster core. 2-Pyr=2-pyridyl.

Towards an understanding of the conjugate addition of organolithium reagents to α,β-unsaturated ketones: the isolation and solid-state structure of a monomeric lithium aluminate with very short agostic Li⋯HC interactions

Abstract Reaction of methylaluminium bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD), 1, with alkyllithium reagents, R′Li (R′=Me, n-Bu or t-Bu), yields the solvent-dependent products lithium bis(2,6-di-tert-butyl-4-methylphenoxide)-THF complex, 2·THF, lithium dimethylbis(2,6-di-tert-butyl-4-methylphenoxide)aluminate, 3, a new type of lithium aluminate in which the lithium centre is stabilised by very short agostic Li⋯H(t-Bu) interactions, and tris(alkyl)aluminium. The observation of these products suggests an explanation for the tendency of α,β-unsaturated ketones to undergo conjugate (rather than 1,2-) addition in the presence of MAD and organolithium reagents.

Deprotonative Metalation of Chloro‐ and Bromopyridines Using Amido‐Based Bimetallic Species and Regioselectivity‐Computed CH Acidity Relationships

A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium-metal combinations. Whereas lithium-zinc and lithium-cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium-copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method.

The first crystallographic evidence for the structures of ortho-lithiated aromatic tertiary amides

Herein is reported the first crystal structures of the products of tertiary amide directed orthometalation reactions. Thus, reaction of N,N-diisopropylbenzamide with tBuLi in di-Et ether gives the corresponding N,N-diisopropyl-2-lithiobenzamide-diethylether complex, 4. Reaction of N,N-diisopropyl-1-naphthamide in THF with tBuLi gives the corresponding N,N-diisopropyl-2-lithionaphthamide-THF complex, 5. The crystal structures of 4 and 5 are presented. [on SciFinder (R)]

Syntheses, structures and magnetic properties of Mn(II) dimers [CpMn(μ-X)]2(Cp = C5H5; X = RNH, R1R2N, CCR)

Manganocene, Cp2Mn, has been employed as a precursor in the synthesis of a range of Mn(II) dimers of the type [CpMn(μ-X)]2 [X = 8-NHC9H6N (1), N(Ph)(C5H4N) (2), N(4-EtC6H4)(C5H4N) (3) and CCPh (4)] as well as the bis-adduct [Cp2Mn{HNC(NMe2)2}2] (5). The solid-state structures of 1–5 are reported. Variable-temperature magnetic measurements have been used to assess the extent of Mn(μ-X)Mn communication within the dimers of 1–4 as a function of the bridging ligands (X).

The first structural studies on trithiocyanuric acid: the solid state structures of its HMPA adduct and its mono-lithiated HMPA complex

Abstract Reaction of BunLi with trithiocyanuric acid (LH3) in toluene/HMPA yielded a mono-lithiated species, [(LH2Li)·HMPA2] (1) shown by X-ray crystallography to have an unprecedented monomeric structure, while crystallisation of trithiocyanuric acid from toluene/HMPA gave a 1:1 adduct, [(LH3)·HMPA] (2), which has an extensive hydrogen-bonded structure governed by N–H⋯S and N–H⋯O interactions; in both 1 and 2 the trithiocyanuric acid unit exists in the thio-keto form in which the hydrogen atoms are nitrogen-bound.

Phosphazene base-promoted halogen–zinc exchange reaction of aryl iodides using diethylzinc

The use of catalytic t-Bu-P4 base dramatically improved the performance of halogen-zinc exchange of aryl iodides, and the arylzinc derivatives were functionalized under copper-free reaction conditions.

Hydration of nitriles to amides by a chitin-supported ruthenium catalyst

Chitin-supported ruthenium (Ru/chitin) promotes the hydration of nitriles to carboxamides under aqueous conditions. The nitrile hydration can be performed on a gram-scale and is compatible with the presence of various functional groups including olefins, aldehydes, carboxylic esters and nitro and benzyloxycarbonyl groups. The Ru/chitin catalyst is easily prepared from commercially available chitin, ruthenium(III) chloride and sodium borohydride. Analysis of Ru/chitin by high-resolution transmission electron microscopy indicates the presence of ruthenium nanoparticles on the chitin support.

Stepwise nucleophilic substitution of manganocene, syntheses and structures of the dimer [CpMn(hpp)]2 and the unusual manganate cage [LiMn(hpp)3]2 (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2,a]pyrimidine)

While the nucleophilic substitution reaction of manganocene [Cp(2)Mn] with Li(hpp) (1 : 1 equivalents) gives the neutral dimer [CpMn(hpp)]2 (1), further substitution of the Cp ligands leads to the unusual dimeric manganate cage compound [LiMn(hpp)3]2 (2), generated by the dimerisation of a simple tris-organomanganate monomer.