Synthesis 2008(1): 94-100  
DOI: 10.1055/s-2007-1000827
PAPER
© Georg Thieme Verlag Stuttgart · New York

An Efficient Synthesis of Novel Dibenzo-Fused Nine-Membered Oxacycles Using a Sequential Baylis-Hillman Reaction and Radical Cyclization

Tirtha Pada Majhia, Arpita Neogia, Soumen Ghoshb, Alok Kumar Mukherjeeb, Madeleine Helliwellc, Partha Chattopadhyay*a
a Division of Chemistry, Indian Institute of Chemical Biology, Kolkata 700 032, India
Fax: +91(33)24735197; e-Mail: partha@iicb.res.in;
b Department of Physics, Jadavpur University, Kolkata 700 032, India
c Department of Chemistry, University of Manchester, Manchester, M13 9PL, UK
Further Information

Publication History

Received 5 September 2007
Publication Date:
07 December 2007 (online)

Abstract

A short and high yield synthetic route to novel dibenz[b,g]oxonins, one of which has been characterized by X-ray crystallography, has been developed based on a sequential Baylis-Hillman reaction and radical cyclization. The regioselective radical cyclization followed a 9-endo-trig pathway.

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Crystal data of 4b: C20H19NO4, MW = 337.4, monoclinic, space group = P21/n, a = 8.186 (5), b = 7.703 (5), c = 26.301 (5) Å, β = 98.59 (1)°, V = 1639.8 (1) Å3, z = 4, F(000) = 712, T = 100 (2) K, µ (MoKα) = 0.096 mm-1. A total 3353 unique reflections were measured (θmax = 26.48°) on a CCD area detector using graphite monochromatized MoKα radiation (λ = 0.71073 Å). The structure was solved by direct methods with SHELXS-97 (Sheldrick, 1997) and refined by full-matrix least-squares method on F2 using SHELXL-97 (Sheldrick, 1997). The non-hydrogen atoms were refined anisotropically and the hydrogen atoms located from the difference Fourier maps were allowed to ride on their parent atoms. Final R1 = 0.0878, wR2 = 0.0816 and GOF = 0.817 for all 3353 observed data. R1 = 0.0439 for 1918 data [F o > 4σ(F o)]. CCDC 649417.