Dizincation and dimagnesiation of benzene using alkali-metal-mediated metallation

Armstrong, David R.; Clegg, William; Dale, Sophie H.; Graham, David V.; Hevia, Eva; Hogg, Lorna M.; Honeyman, Gordon W.; Kennedy, Alan R.; Mulvey, Robert E.

doi:10.1039/b613655a

Cited by 63 publications

(48 citation statements)

References 10 publications

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“…The naphthalene skeleton represents a popular unit in chemical and pharmaceutical industries with interesting optical, electronic and biological properties. 121 Synergically-operative metallators such as sodium zincate (TMEDA)$Na(m-TMP)(m-t Bu) Zn( t Bu) [149][150][151][152][153][154][155] or sodium manganate (TMEDA)$Na(m-TMP)(m-CH 2 SiMe 3 )Mn(TMP) 119,156-159 offer an enhanced regioselectivity. Directed metallation of activated naphthalene derivatives with alkyllithium reagents akin to the Directed ortho Metallation (DoM) 118,132-146 of activated benzene derivatives has been shown to provide access to functionalized naphthalene compounds.…”

Section: Resultsmentioning

confidence: 99%

Pre-inverse-crowns: synthetic, structural and reactivity studies of alkali metal magnesiates primed for inverse crown formation

et al. 2014

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Two new alkali metal monoalkyl-bisamido magnesiates, the potassium compound [KMg(TMP) 2 n Bu] and its sodium congener [NaMg(TMP) 2 n Bu] have been synthesised in crystalline form (TMP ¼ 2,2,6,6tetramethylpiperidide). Devoid of solvating ligands and possessing excellent solubility in hydrocarbon solvents, these compounds open up a new gateway for the synthesis of inverse crowns. X-ray crystallography established that [KMg(TMP) 2 n Bu] exists in three polymorphic forms, namely a helical polymer with an infinite KNMgN chain, a hexamer with a 24-atom (KNMgN) 6 ring having endo-disposed alkyl substituents, and a tetramer with a 16-atom (KNMgN) 4 ring also having endo-disposed alkyl substituents. Proving their validity as pre-inverse-crowns, both magnesiates react with benzene and toluene to generate known inverse crowns in syntheses much improved from the original, supporting the idea that the metallations take place via a template effect. [KMg(TMP) 2 n Bu] reacts with naphthalene to generate the new inverse crown [KMg(TMP) 2 (2-C 10 H 7 )] 6 , the molecular structure of which shows a 24-atom (KNMgN) 6 host ring with six naphthalene guest anions regioselectively magnesiated at the 2-position. An alternative unprecedented 1,4-dimagnesiation of naphthalene was accomplished via [NaMg(TMP) 2 n Bu] and its NaTMP co-complex "[NaMg(TMP) 2 n Bu]$NaTMP", manifested in [{Na 4 Mg 2 (TMP) 4 (2,2,6trimethyl-1,2,3,4-tetrahydropyridide) 2 }(1,4-C 10 H 6 )]. Adding to its novelty, this 12-atom (NaNNaNMgN) 2 inverse crown structure contains two demethylated TMP ligands as well as four intact ones. Reactivity studiesshow that the naphthalen-ide and -di-ide inverse crowns can be regioselectively iodinated to 2-iodo and 1,4-diiodonaphthalene respectively.Scheme 1 Synthesis of inverse crown complexes 1a/b and 2a/b (for a R ¼ H; for b R ¼ Me).

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Section: Resultsmentioning

confidence: 99%

Pre-inverse-crowns: synthetic, structural and reactivity studies of alkali metal magnesiates primed for inverse crown formation

et al. 2014

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“…Recently we reported a sodium modification of 1 , [(TMEDA)Na(TMP)( t Bu)Zn( t Bu)] ( 1-Na ) (TMEDA= N , N , N ′, N ′-tetramethylethylenediamine) 11 which exhibits an enhanced metalating power, successfully accomplishing not only monometalation but also regioselective dimetalation of nonactivated arenes such as benzene 12 or naphthalene. 13 The heteroleptic nature of the TMP-zincates 1 and [(TMEDA)Na(TMP)( t Bu)Zn( t Bu)] ( 1-Na ) makes it possible that they can perform as either alkyl or amido bases.…”

Section: Introductionmentioning

confidence: 99%

Closer Insight into the Reactivity of TMP−Dialkyl Zincates in Directed ortho-Zincation of Anisole: Experimental Evidence of Amido Basicity and Structural Elucidation of Key Reaction Intermediates

et al. 2009

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The new dialkyl(aryl) lithium zincates [(THF)2Li(C6H4−OMe)MeZnMe] (4), [(TMEDA)Li(C6H4−OMe)MeZnMe] (6), [(THF)3Li(C6H4−OMe)tBuZntBu] (7), and [(PMDETA)Li(C6H4−OMe)tBuZntBu] (8) have been prepared by co-complexation reactions of lithiated anisole with the relevant dialkylzinc compound and the relevant Lewis base. These new heterobimetallic compounds have been characterized in solution using 1H, 13C{H}, and 7Li NMR spectroscopy, and the molecular structures of 6 and 8 have been elucidated by X-ray crystallography. In 6 the distinct metals are connected through the anisole ligand which binds in an ambidentate fashion (through carbon−zinc and oxygen−lithium contacts) and also through one of the methyl groups, to close a [LiOCCZnC] six-membered ring; whereas 8 displays an open structure where anisole connects the two metals (in the same mode as in 6) but with the tert-butyl groups exclusively bonded terminally to zinc. Reactivity studies of zincates 4 and 7 with the amine TMP(H) supply experimental evidence that these heterobimetallic compounds are intermediates in the two-step deprotonation reaction of anisole by TMP−dialkyl zincates and show the relevance of the alkyl groups in the efficiency of TMP−dialkyl zincate bases. In addition, important solvent effects have also been evaluated. When hexane is added to THF solutions of compounds 4 or 7, the homoleptic tetraorganozincate [(THF)2Li2Zn(C6H4−OMe)4] (5) is obtained as the result of a disproportionation process. This lithium-rich zincate has also been spectroscopically and crystallographically characterized.

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“…Reagent 1 is a structurally well-defined crystalline compound [25] and efficient metallating (zincating) agent [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] [most recently with Nheterocyclic carbenes (NHCs) [42] ] though it has occasionally also been utilized as a nucleophilic t-butyl source. [43][44] Reagent 2 is a putative compound in that it has only been generated in situ by mixing LiTMP, Bu [45][46][47][48][49] which has been extensively studied.…”

Section: Resultsmentioning

confidence: 99%

Heterobimetallic metallation studies of N,N-dimethylphenylethylamine (DMPEA): benzylic C–H bond cleavage/dimethylamino capture or intact DMPEA complex

et al. 2015

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Dizincation and dimagnesiation of benzene using alkali-metal-mediated metallation

Cited by 63 publications

References 10 publications

Pre-inverse-crowns: synthetic, structural and reactivity studies of alkali metal magnesiates primed for inverse crown formation

Pre-inverse-crowns: synthetic, structural and reactivity studies of alkali metal magnesiates primed for inverse crown formation

Closer Insight into the Reactivity of TMP−Dialkyl Zincates in Directed ortho-Zincation of Anisole: Experimental Evidence of Amido Basicity and Structural Elucidation of Key Reaction Intermediates

Heterobimetallic metallation studies of N,N-dimethylphenylethylamine (DMPEA): benzylic C–H bond cleavage/dimethylamino capture or intact DMPEA complex

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