Synthesis 2007(15): 2379-2387  
DOI: 10.1055/s-2007-983773
PAPER
© Georg Thieme Verlag Stuttgart · New York

The High Stereoselectivity of the Tandem Sequence Diels-Alder Reaction/Ireland­-Claisen Rearrangement Starting from Substituted O-(E)-Buta-1,3-dienyl Ketene Acetals and Cyclic Dienophiles

Nicolas Soldermanna, Jörg Velkerb, Antonia Neelsc, Helen Stoeckli-Evansc, Reinhard Neier*d
a Novartis Institutes for BioMedical Research Basel, Global Discovery Chemistry, Lichtstraße 35, 4056 Basel, Switzerland
b Actelion Pharmaceuticals Ltd., Innovation Centre, 4123 Allschwil, Switzerland
c Institut de Microtechnique, Université de Neuchâtel, rue Emile-Argand 11, case postale 158, 2009 Neuchâtel, Switzerland
d Institut de Chimie, Université de Neuchâtel, rue Emile-Argand 11, case postale 158, 2009 Neuchâtel, Switzerland
Fax: +41(32)7182511; e-Mail: reinhard.neier@unine.ch;
Further Information

Publication History

Received 9 January 2007
Publication Date:
12 July 2007 (online)

Abstract

A new tandem reaction leads to bicyclic cyclohexene derivatives with complete control of the relative configuration of the four chiral centers formed. The high diastereoselectivity is the consequence of an endo-selective Diels-Alder reaction followed by an Ireland-Claisen rearrangement that proceeds via a boat-like transition state.

7

Crystal structure analysis of 2f: C20H25NO4Si, M r = 371.50, monoclinic, space group P21, a = 8.191(1), b = 23.442(2), c = 11.342(1) Å, β = 105.12(1)°, V = 2102.4(3) Å3, Z = 4, ρcalcd = 1.174 g cm-3, T = 223(2) K, µ = 1.34 cm-1, λ = 0.71073 Å, 1.65 ≤ θ ≤ 26.05°, Stoe IPDS diffractometer, crystal dimensions 0.65 × 0.40 × 0.15 mm; 7956 independent reflections, 3934 observed reflections with [I > 2σ(I)]; R-values [I > 2σ(I)]: R 1 = 0.0658, wR 2 = 0.1409.
Crystal structure analysis of 4: C24H18N2O6, M r = 430.40, triclinic, space group P, a = 7.894(2), b = 11.426(3), c = 12.057(4)Å, α = 101.78(4), β = 97.43(4), χ = 98.91(3)°, V = 1037.2(5) Å3, Z = 2, ρcalcd = 1.378 g cm-3, T = 293(2) K, µ = 1.01 cm-1, λ = 0.71073 Å, 1.65 ≤ θ ≤ 26.05°, Stoe IPDS diffractometer, crystal dimensions 0.70 × 0.50 × 0.40 mm; 3738 independent reflections, 2453 observed reflections with [I > 2σ(I)]; R-values [I > 2σ(I)]: R 1 = 0.0328, wR 2 = 0.0816.
Crystal structure analysis of 5: C24H18N2O6·CHCl3, M r = 549.77, triclinic, space group P, a = 10.261(3), b = 11.610(3), c = 11.818(4)Å, α = 76.81(3), β = 67.38(3), χ = 87.40(2)°, V = 1263.9(7) Å3, Z = 2, ρcalcd = 1.445 g cm-3, µ = 1.34 cm-1, λ = 0.71073 Å, 2.00 ≤ θ ≤ 25.50°, Stoe AED2 diffractometer, crystal dimensions 0.65 × 0.49 × 0.23 mm; 4709 independent reflections, 3504 observed reflections with [I > 2σ(I)]; R-values [I > 2σ(I)]: R 1 = 0.0701, wR 2 = 0.1669.
All three structures were refined with full-matrix block least squares on F 2; all non-hydrogen atoms were anisotropically refined. Crystallographic data (excluding structure factors)for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-118778 for 1f, CCDC-629878 for 2f, CCDC-629879 for 3c, CCDC-629880 for 4 and CCDC-629881 for 5. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: +44(1223)336033; e-mail: deposit@ccdc.cam.ac.uk.