Acidities of carbon and nitrogen acids: the aromaticity of the cyclopentadienyl anion

Bordwell, F. G.; Drucker, George E.; Fried, Herbert E.

doi:10.1021/jo00316a032

Cited by 245 publications

(166 citation statements)

References 5 publications

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Section: Resultsmentioning

confidence: 99%

“…The pK a of maleimide NH is around 10,33 hence it can be deprotonated easily in the presence of K 2 CO 3 to give the corresponding anion 20, which reacted with alkyl bromide to give N-substituted product 21. However, the pK a of an indole NH is about 21,33 so for deprotonation it requires bases with a pK a higher than 21. When arcyriarubin A was treated with strong bases such as NaH, all three NHs were completely deprotonated to afford the trianion 22 presumably (Scheme 3), 34,35 which reacted with alkyl bromide to give the N,O-dialkylated product 23.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Protecting-group-free synthesis of the bisindolylmaleimide GF109203X

Gao¹,

Jia²,

Li³

et al. 2015

Arkivoc

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The bisindolylmaleimide GF109203X is a highly selective inhibitor to Protein Kinase C (PKC) and has attracted much attention. However, its reported synthesis required protecting groups. In order to achieve a short and N-protecting-group-free synthesis of GF109203X, an investigation on N-alkylation of arcyriarubin A was carried out using different bases, solvents and equivalents of bromododecane. It is found that mono-N-alkylation and mono-N'-alkylation could be achieved respectively. Thus, a protecting-group-free synthesis of GF109203X was accomplished in 40% overall yield starting from indole. This work will lead to a short synthesis of mono-N'-alkylated arcyriarubins to accelerate drug discovery.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Protecting-group-free synthesis of the bisindolylmaleimide GF109203X

Gao¹,

Jia²,

Li³

et al. 2015

Arkivoc

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“…This solid, which was also insoluble in polar solvents like THF, did not contain the DIPP-nacnac ligand and was probably polymeric (H 2 NCaNH 2 BH 3 ) 1 . Protonation of the DIPP-nacnac anion by NH 3 was unexpected and seemed thermodynamically unfavorable: the pK a value of NH 3 (41) [12] is substantially higher than the pK a value of the b-diketimine DIPP-nacnacH (estimated at < 30). However, this reaction is possibly predetermined by a non-classical N À H···C interaction, as observed in the crystal structure of (Figure 1 a).…”

Section: Thermal Decomposition Of Ca(dippmentioning

confidence: 93%

Calcium–Amidoborane–Ammine Complexes: Thermal Decomposition of Model Systems

Harder¹,

Spielmann

Tobey

2012

Chemistry A European J

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Hydrocarbon-soluble model systems for the calcium-amidoborane-ammine complex Ca(NH(2)BH(3))(2)⋅(NH(3))(2) were prepared and structurally characterized. The following complexes were obtained by the reaction of RNH(2)BH(3) (R = H, Me, iPr, DIPP; DIPP = 2,6-diisopropylphenyl) with Ca(DIPP-nacnac)(NH(2))⋅(NH(3))(2) (DIPP-nacnac = DIPP-NC(Me)CHC(Me)N-DIPP): Ca(DIPP-nacnac)(NH(2)BH(3))⋅(NH(3))(2), Ca(DIPP-nacnac)(NH(2)BH(3))⋅(NH(3))(3), Ca(DIPP-nacnac)[NH(Me)BH(3)]⋅(NH(3))(2), Ca(DIPP-nacnac)[NH(iPr)BH(3)]⋅(NH(3))(2), and Ca(DIPP-nacnac)[NH(DIPP)BH(3)]⋅NH(3). The crystal structure of Ca(DIPP-nacnac)(NH(2)BH(3))⋅(NH(3)(3) showed a NH(2)BH(3)(-) unit that was fully embedded in a network of BH⋅⋅⋅HN interactions (range: 1.97(4)-2.39(4) Å) that were mainly found between NH(3) ligands and BH(3) groups. In addition, there were N-H⋅⋅⋅C interactions between NH(3) ligands and the central carbon atom in the ligand. Solutions of these calcium-amidoborane-ammine complexes in benzene were heated stepwise to 60 °C and thermally decomposed. The following main conclusions can be drawn: 1) Competing protonation of the DIPP-nacnac anion by NH(3) was observed; 2) The NH(3) ligands were bound loosely to the Ca(2+) ions and were partially eliminated upon heating. Crystal structures of [Ca(DIPP-nacnac)(NH(2)BH(3))⋅(NH(3))](∞), Ca(DIPP-nacnac)(NH(2)BH(3))⋅(NH(3))⋅(THF), and [Ca(DIPP-nacnac){NH(iPr)BH(3)}](2) were obtained. 3) Independent of the nature of the substituent R in NH(R)BH(3), the formation of H(2) was observed at around 50 °C. 4) In all cases, the complex [Ca(DIPP-nacnac)(NH(2))](2) was formed as a major product of thermal decomposition, and its dimeric nature was confirmed by single-crystal analysis. We proposed that thermal decomposition of calcium-amidoborane-ammine complexes goes through an intermediate calcium-hydride-ammine complex which eliminates hydrogen and [Ca(DIPP-nacnac)(NH(2))](2). It is likely that the formation of metal amides is also an important reaction pathway for the decomposition of metal-amidoborane-ammine complexes in the solid state.

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“…This corresponds to a free energy difference at 25°C of 6.8 kcal/mol. In contrast, the energetic advantage of having a negative charge in an indenyl ring system can be evaluated from the pK value (= 20.1) of indene, resulting in an estimated aromatic stabilization energy of 20 kcal/mol (22 For personal use only. a-energy are lost as a pair of electrons is removed from the a-system.…”

Section: Rates Of the Thermal Decomposition Of The Diazoindenesmentioning

confidence: 99%

Substituent effects on the rate of carbene formation in the pyrolysis of indenyl diazo compounds

Kapur¹,

Mathur²,

McManus³

et al. 1988

Can. J. Chem.

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. 66, 2888 (1988). Rate constants for the pyrolysis of the indenyl diazo compounds, 5a-5e, in methanol have been determined and correlated with a + , giving a p+ = -0.76. The product of this pyrolysis reaction is the methyl ether resulting from trapping at the carbenic centre. The mechanism proposed for this process involves rate-determining unimolecular loss of nitrogen by the allowed nonlinear pathway to form the singlet u 2 carbene. Evidence presented implies that this singlet state is more stable than the p2 state despite the difference in aromatic stabilization of the two.

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Acidities of carbon and nitrogen acids: the aromaticity of the cyclopentadienyl anion

Cited by 245 publications

References 5 publications

Protecting-group-free synthesis of the bisindolylmaleimide GF109203X

Protecting-group-free synthesis of the bisindolylmaleimide GF109203X

Calcium–Amidoborane–Ammine Complexes: Thermal Decomposition of Model Systems

Substituent effects on the rate of carbene formation in the pyrolysis of indenyl diazo compounds

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