The O-substitution Pattern of the MoCl₅-Mediated Oxidative Aryl-Aryl Coupling Reaction

Abstract

Different protective groups for the phenolic oxygen were investigated in the molybdenum pentachloride-mediated dehydro-dimerization reaction. Cyclic acetals and ketals, triisopropylsilyl and alkoxycarbonylmethyl moieties are compatible with the strong acidic reaction conditions.

Key words

biaryls - coupling - dimerizations - protective groups - molybdenum

References

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2

Kramer, B.; Averhoff, A.; Waldvogel, S. R. Angew. Chem. Int. Ed. 2002, 41: in press.

17

X-ray crystal structure analysis of 4: formula C₂₆H₃₀O₆ M = 438.50 colorless crystal 0.35 × 0.30 × 0.10 mm a = 11.923(2) b = 12.352(2) c = 16.974(2) Å α = 96.80(1) β = 92.64(2) γ = 112.76(1)° V = 2277.4(6) Å3 ρcalc = 1.279 gcm^-3 µ = 7.34 cm^-1 empirical absorption correction via ψ scan data (0.783 ≤ T ≤ 0.930) Z = 4 triclinic space group P1bar (No. 2) λ = 1.54178 Å T = 223 K ω/2θ scans 9478 reflections collected (+h ±k ±l) [(sinθ)/λ] = 0.62 Å-1 9040 independent (Rint = 0.026) and 7595 observed reflections [I ≥ 2 σ(I)] 595 refined parameters R = 0.047 wR2 = 0.134 max. residual electron density 0.30 (-0.24) e Å^-3 two independent molecules in the asymmetric unit hydrogens calculated and refined as riding atoms.
Data set was collected with an Enraf Nonius CAD4 diffractometer. Programs used: data collection Express (Nonius B.V. 1994) data reduction MolEN (K. Fair 1990) structure soln SHELXS-97 (Sheldrick, G. M. Acta Cryst. 1990, A46, 467) structure refinement SHELXL-97 (Sheldrick, G. M. Universität Göttingen, 1997) graphics POV-Ray 3.2.
Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication CCDC 191456. Copies of the data can be obtained free of charge on application to The Director CCDC 12 Union Road CambridgeCB2 1EZ UK [fax: [phone] e-mail: [e-mail]].

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Structure of 4: The chemical shifts for the structure were assigned by long range coupling experiments and refer to the following numbering (Figure [2] ).