The Mechanism of the Stobbe Condensation

Johnson, William S.; McCloskey, A. L.; Dunnigan, Daniel A.

doi:10.1021/ja01157a133

Cited by 26 publications

(25 citation statements)

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“…experimental). The predominance of this configuration parallels our recently reported observations [1, 21, and can be interpreted in terms of the mechanism of the Stobbe condensation [7,81, which in the present case wouldinvolve the formation of the diastereoineric S-lactonic intermediates 8 and 9. The steric course of condensation will be controlled by the initial attack by the ester carbanion on the ketone.…”

Section: -242 282-285 and -300-310;supporting

confidence: 92%

Condensation of Aryl Benzyl Ketones with Dimethyl Diglycollate

El-Newaihy¹,

Salem²,

Enayat³

et al. 1980

J. Prakt. Chem.

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Section: -242 282-285 and -300-310;supporting

confidence: 92%

Condensation of Aryl Benzyl Ketones with Dimethyl Diglycollate

El-Newaihy¹,

Salem²,

Enayat³

et al. 1980

J. Prakt. Chem.

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“…In this case, however, any rotation about the C(3)-C(4) bond is prohibited, so the relief of the strain can be achieved via changes of the bond angles at these two carbon atoms. This is demonstrated by the dramatic increase of the exocyclic bond angles C 3 7178.3 165.1 5-2.9 -8.7(1) 173.7(5) -174.6(4) 5.6(7) 177.6(5) -2.6(7) -172.6(5) -177.4 (5) 169.8(6) -9.0(9) -39. (in 1 105.5(2)" and 2 116.9(4)").…”

Section: Molecular Structuresmentioning

confidence: 99%

Photochromic systems. Part 1. Structural and spectroscopic study of photochromically active products of Stobbe condensation. 2,3-Dibenzylidenesuccinic acid and its anhydride

Davidse¹,

Dillen²,

Heyns³

et al. 1990

Can. J. Chem.

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E,E-2,3-Dibenzylidenesuccinic acid (2) and its anhydride (1) were synthesized, their crystal structures and 1H and 13C nuclear magnetic resonance spectra were determined, and electron charge densities of carbon atoms were calculated. These results were related to the corresponding data available for E-cinnamic acid (3) in order to evaluate the effect of structural changes in a series 3 → 2 → 1 on the molecular parameters and spectroscopic properties of the cinnamic system. In the molecule of 2 most of the steric strain is released by the rotation about the C(α)—C(α′) bond giving rise to a structure consisting of two, approximately independent, cinnamic acid moieties. In 1, severe steric strain is introduced, as demonstrated by the unusually large values of the CCC bond angles exocyclic with respect to the anhydride ring, as well as by significant deviations from the plane of the cinnamic skeleton. The geometry of 1 results in an intramolecular shielding of the aromatic hydrogen atoms due to the proximity of the two benzene rings; this shielding effect for the ortho, meta, and para hydrogen atoms correlates well with the intramolecular distances between the corresponding positions of both rings. The common linear relationship between 13C chemical shifts and the electron charge densities on the given carbon atom has been obtained for compounds 1, 2, and 3.Crystal data. Anhydride (1): space group P21/c with a = 13.536(3), b = 14.391(3), c = 7.159(1) Å; β = 98.69(1)°; Rw = 0.029 and R = 0.055. Succinic acid (2): space group [Formula: see text] with a = 8.881(3), b = 9.786(1), c = 11.355(3) Å; α = 85.56(1), β = 88.76(2), γ = 69.46(2)°; Rw = 0.048 and R = 0.081. This compound cocrystallizes with one molecule of the solvent (acetic acid). Keywords: photochromic, cinnamic, succinic.

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“…As outlined in Scheme 1, the synthesis of 8 began with 5-methyl-4-(carboxymethyl)benzoic acid (9), which was prepared in two steps from commercially available 6-methylindan-1-one according to a procedure described in [17]. Conversion to di(tert-butyl)-protected 10 was attempted unsuccessfully by three different approaches: t BuOK/oxalyl chloride; isobutylene/H 2 SO 4 [18], and tert-butyl 2,2,2-trichloroacetimidate/BF 3 ¥ OEt 2 [19]. Surprisingly, replacement of BF 3 ¥ OEt 2 with BBr 3 , provided product 10 in good yield (83%), as did the use of in situ generated isobutylene, prepared with t BuOH in the presence of H 2 SO 4 adsorbed onto MgSO 4 [20] (71% yield).…”

mentioning

confidence: 99%

Enantioselective Synthesis of (S)‐3‐Carboxy‐4‐((carboxy)difluoromethyl)phenylalanine in Protected Form and Its Incorporation into a PTP‐1B‐Directed Tripeptide

Kang

Gao

et al. 2004

Chemistry & Biodiversity

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Recent findings have shown that, when expressed in the tripeptide platform, 'Fmoc-Glu-Xxx-Leu-amide', the phosphotyrosyl mimetic (pTyr), Xxx=(S)-3-carboxy-4-(carboxymethyl)-Phe, provides higher PTP-1B affinity than that obtained with Xxx=(S)-difluorophosphonomethyl-Phe (F(2)Pmp). This was of note, since difluorophosphonomethyl-containing pTyr mimetics have typically exhibited higher PTP-inhibitory potencies than carboxy-based mimetics, indicating the potential value of 3-carboxy-4-(carboxymethyl)-Phe as a starting point for further analogue development. Therefore, relying on precedence that alpha-fluorination often enhances PTP-1B affinity, (S)-3-carboxy-4-((carboxy)difluoromethyl)-Phe was designed as a PTP-1B-directed pTyr mimetic. Reported herein is the synthesis of this new amino acid analogue through application of commercially available Williams chiral auxiliary. The target was prepared in an orthogonally protected form suitable for peptide synthesis according to Fmoc chemistries and utilization for the synthesis of a PTP-1B-directed tripeptide bearing the sequence indicated above. Biological evaluation with in vitro PTP-1B assays indicated nearly total loss of affinity for this peptide. Evidence is provided that the unexpected deleterious effect of fluorination is probably not related to pK(a) effects.

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The Mechanism of the Stobbe Condensation

Cited by 26 publications

References 0 publications

Condensation of Aryl Benzyl Ketones with Dimethyl Diglycollate

Condensation of Aryl Benzyl Ketones with Dimethyl Diglycollate

Photochromic systems. Part 1. Structural and spectroscopic study of photochromically active products of Stobbe condensation. 2,3-Dibenzylidenesuccinic acid and its anhydride

Enantioselective Synthesis of (S)‐3‐Carboxy‐4‐((carboxy)difluoromethyl)phenylalanine in Protected Form and Its Incorporation into a PTP‐1B‐Directed Tripeptide

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