Catalytic 2,3,4-hexatriene formation by terminal alkyne coupling at calcium

Barrett, Anthony G. M.; Crimmin, Mark R.; Hill, Michael S.; Hitchcock, Peter B.; Lomas, Sarah L.; Procopiou, Panayiotis A.; Suntharalingam, Kogularamanan

doi:10.1039/b818848c

Cited by 36 publications

(40 citation statements)

References 24 publications

(21 reference statements)

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“…Table 5, entry 1). 8 This catalytic protocol has now been extended to a wider range of alkaline-earth precatalysts, and alkyne substrate types and the results are presented in Tables 5 and 6. For complex XV, it was observed that turnover was accompanied by significant amounts of ligand redistribution to yield the homoleptic species [{(2,6-i Pr 2 C 6 H 3 ) 2 N 3 } 2 Ca(THF) 2 ] and, presumably, polymeric [Ca{CCCH 2 OMe} 2 ] n .…”

Section: ■ Introductionmentioning

confidence: 98%

“…8 With this in mind, the catalytic dimerization reactions of phenyl propargyl ether and 3-dimethylamino-1-propyne were attempted using the same conditions identified for successful methyl propargyl ether coupling. In both cases analysis by 1 H NMR spectroscopy confirmed the clean formation of the desired butatriene products, each of which displayed characteristic triplet and doublet resonances (1,6-diphenoxy-2,3,4-hexatriene, δ H 6.44 (t, 2H), 5.10 ppm (d, 4H); 1,6-bis(dimethylamino)-2,3,4-hexatriene, δ H 5.92 (t, 2H), 5.12 ppm (d, 4H)).…”

Section: ■ Introductionmentioning

confidence: 99%

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Catalytic and Stoichiometric Cumulene Formation within Dimeric Group 2 Acetylides

et al. 2013

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A series of β-diketiminate-supported magnesium and calcium acetylide complexes have been synthesized by σ-bond metathesis of magnesium n-butyl or magnesium and calcium amido precursors and a range of terminal acetylenes. The dimeric complexes have been characterized by NMR spectroscopy and X-ray diffraction analysis. The homoleptic bis(amido) and dialkyl complexes [M{X-(SiMe 3 ) 2 } 2 (THF) 2 ] (M = Ca, Sr; X = N, CH) have been assessed for the atom-efficient, catalytic head-to-head dimerization of donorfunctionalized terminal alkynes into butatrienes and aryl-/silylsubstituted terminal acetylenes into 1,3-enynes. Deuterium labeling studies of the catalytic reactions are suggested to imply that triene formation requires concerted proton delivery and rearrangement via an adjacent methylene group at a bimetallic alkaline-earth species. ■ INTRODUCTIONDespite recent and growing interest, the chemistry of σ-organometallic derivatives (i.e., containing a direct metal to carbon σ bond) of the heavier alkaline-earth elements, Ca, Sr, and Ba, is still relatively underdeveloped. Among derivatives of this type, however, σ-bonded acetylides occupy something of a privileged position as the relatively low pK a of terminal alkynes not only confers thermodynamic stability to σ-bonded group 2 complexes, through charge stabilization in the highly ionic complexes formed upon deprotonation, but also allows facile synthesis through reaction with a suitably basic group 2 precursor.Originally reported in 1971 by Coles and co-workers, 1 the homoleptic acetylides [M(CCPh) 2 ] n (M = Ca, Sr, Ba) are relatively intractable polymeric materials, which depolymerize slowly upon dissolution in the coordinating solvent tetrahydrofuran. More tractable and soluble materials may be isolated by synthesis of heteroleptic species supported by sterically demanding and lipophilic coligands. Hanusa reported the synthesis of heteroleptic calcium acetylides [Cp′Ca(C CR)(THF)] 2 such as I from deprotonation of RCCH with [(Cp′)Ca{N(SiMe 3 ) 2 }(THF) 2 ] (Cp′ = i Pr 4 C 5 H). 2 These compounds were shown to be dimeric in the solid state with μ 2 -C α acetylide units asymmetrically bridging the two calcium centers. Despite the presence of the sterically demanding Cp′ ligand, solution studies revealed a propensity for these species to undergo undesired Schlenk-like equilibria, limiting studies of these compounds. Ruhlandt-Senge has reported the rational synthesis of a series of homoleptic heavier alkaline-earth acetylides of the formula [(18-crown-6)M(CCSiPh 3 ) 2 ] (II− IV) through the deprotonation of the terminal acetylene with the appropriate group 2 bis(trimethylsilyl)amide [M{N-(SiMe 3 ) 2 } 2 ] 2 in the presence of 18-crown-6. 3 Most recently, the same group has discussed the bonding within these and similar species in an attempt to rationalize observed distortions from the more symmetrical geometries predicted by valence shell electron pair repulsion (VSEPR) theory. 4 Combined synthetic and DFT studies concluded that distortions from linearity were ...

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Section: ■ Introductionmentioning

confidence: 98%

Section: ■ Introductionmentioning

confidence: 99%

Catalytic and Stoichiometric Cumulene Formation within Dimeric Group 2 Acetylides

et al. 2013

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“…( 12)) [49]. Moreover, dimerization reaction of the electron-enriched terminal alkyne 3methoxyprop-1-yne was also reported and it led to a fancy molecule 1,6-dimethoxyhexa-2,3,4-triene bearing three cumulated C@C bonds in the presence of Ca complex catalysts [50].…”

Section: Ca-catalyzed Reactions Of Cah and Si-hmentioning

confidence: 98%

Calcium-catalyzed reactions of element-H bonds

Qian²,

Deng

et al. 2018

Science Bulletin

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“…The reaction was proposed to occur via a dimeric calcium acetylide intermediate and to be promoted by polarisation of the electron density within the alkynide CRC bonds. 182 Calcium reagents Ca(a-Me 3 Si-2-Me 2 Nbenzyl) 2 .2THF and [Ca{N(SiMe 3 ) 2 } 2 .2THF] have been reacted with partially dehydroxylated silica to afford materials that calcium fragments, which have been shown to be active for olefin hydrosilylation, intramolecular hydroamination, and styrene polymerisation. 183 The decomposition route of calcium primary amidoborane complexes has been reported to depend on the steric bulk of the amidoborane substituent.…”

Section: Group 16 Donorsmentioning

confidence: 99%

“…141 The application of Group 2 complexes in molecular catalysis has also continued to attract intense international attention. 105,152,[175][176][177][178][179][180][181][182][183]…”

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confidence: 99%

Alkaline and alkaline earth metals

Hill¹

2010

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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This chapter provides a non-critical overview of research advances involving the elements of Groups 1 and 2 during the calendar year 2009. As was the case in previous years, coverage will concentrate upon topics centred around the synthesis, structures and applications of coordination compounds of these elements. This self-imposed restriction will necessarily result in the omission of numerous advances in other branches of chemistry and, for this, the author wishes to apologise in advance. HighlightsConcerns over energy supply and storage have resulted in enhanced interest in the application of s-block compounds, either as components of MOF structures or in the synthesis of amidoborane derivatives, as hydrogen storage media. [10][11][12]83,[124][125][126] The study of lower oxidation state alkaline earth [M(I)] species has also gathered momentum with reports of further examples of Mg-Mg bonded species and their reactivity, [129][130][131][132] as well as a unique Ca(I) complex. 141 The application of Group 2 complexes in molecular catalysis has also continued to attract intense international attention. 105,152,[175][176][177][178][179][180][181][182][183]

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Catalytic 2,3,4-hexatriene formation by terminal alkyne coupling at calcium

Cited by 36 publications

References 24 publications

Catalytic and Stoichiometric Cumulene Formation within Dimeric Group 2 Acetylides

Catalytic and Stoichiometric Cumulene Formation within Dimeric Group 2 Acetylides

Calcium-catalyzed reactions of element-H bonds

Alkaline and alkaline earth metals

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