Synthesis of novel steroid backbones via photoinduced electron transfer initiated domino cyclizations of silyl enol ethers

Bunte JO, Rinne S, Mattay J. Synthesis of novel steroid backbones via photoinduced electron transfer initiated domino cyclizations of silyl enol ethers. SYNTHESIS-STUTTGART. 2004;(4):619-633.Photoinduced electron transfer was used to activate silyl enol ethers. The generated radical cations of specifically designed precursors undergo ring closure reactions to yield novel steroid compounds. These domino reactions proceed with high stereo-selectivity. The synthesis of the complex silyl enol ethers, the stereo-selective domino cyclization process and the assignment of stereochemistry of the novel steroid compounds is presented

Cyclizations of silyl enol ether radical cations - The cause of the stereoselectivity

Bunte JO, Heilmann EK, Hein B, Mattay J. Cyclizations of silyl enol ether radical cations - The cause of the stereoselectivity. EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2004;2004(16):3535-3550.We have used photoinduced electron transfer (PET) activation of silyl enol ethers for the synthesis of tricyclic hydrocarbons. The mechanism of this reaction was investigated by conducting independent radical-induced cyclizations of corresponding iodo ketones and performing density functional theory (DFT) calculations on the possible intermediates. Our aim was to explain the nature of the reactive intermediate of the cyclization step and to find the causes of the various types of selectivity observed in this process. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004

Synthesis and PET oxidative cyclization of silyl enol ethers: build-up of quasi-steroidal carbocycles

Bunte JO, Rinne S, Schafer C, Neumann B, Stammler H-G, Mattay J. Synthesis and PET oxidative cyclization of silyl enol ethers: build-up of quasi-steroidal carbocycles. TETRAHEDRON LETTERS. 2003;44(1):45-48.PET oxidative cyclization of silyl enol ethers carrying suitable side chains with olefinic double bonds results in the stereoselective formation of carbocycles. Two model compounds for investigating the influence of silyl enol ether ring size are synthesized. Furthermore the synthesis of a quasi-steroidal carbocycle with an unnatural configuration is presented. (C) 2002 Elsevier Science Ltd. All rights reserved