A. Baranovsky, D. A. Bolibrukh, J. Bull
2007
Citations
0
Influential Citations
15
Citations
Journal
European Journal of Organic Chemistry
Abstract
The Diels–Alder reaction of 3-methoxyestra-1,3,5(10),14,16-pentaen-17-yl acetate (1) with nitroethylene gives 3-methoxy-16-nitro-14,17-ethenoestra-1,3,5(10)-trien-17β-yl acetate (2). Cycloadduct 2 can be reduced with TiCl3, giving oxazine 3 as a result of sigmatropic rearrangement, whereas the treatment of 2 with Lewis acids (TiCl4, SnCl4) leads to a derivative of the cyclic hydroximic acid 10; the latter is viewed as a product of intramolecular rearrangement. Cycloadduct 2 suffers a weak base-induced cleavage of the C(16)–C(17) bond, releasing the nitrile oxide intermediate, which can be trapped by a dipolarophile or reduced with triphenylphosphane. Thus, the trapping of the nitrile oxide with propargyl alcohol gives the isoxazole 12 in 50 % yield, and the reduction of the nitrile oxide with triphenylphosphane gives nitrile 9 in 94 % yield. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)