Synlett 2007(5): 0669-0685  
DOI: 10.1055/s-2007-970777
ACCOUNT
© Georg Thieme Verlag Stuttgart · New York

Rearrangement and Cyclization Reactions by Photoinduced Electron Transfer: New Approaches for the Synthesis of Polycyclic Compounds

Prashant A. Waske, Nikolay T. Tzvetkov, Jochen Mattay*
Fakultät für Chemie, Universität Bielefeld, Postfach 100 131, 33501 Bielefeld, Germany
Fax: +49(521)1066417; e-Mail: mattay@uni-bielefeld.de;
Further Information

Publication History

Received 2 August 2006
Publication Date:
08 March 2007 (online)

Abstract

The concept of intramolecular radical ion cyclization reactions by photoinduced electron transfer (PET) is a powerful tool for constructing complex carbocyclic and heterocyclic ring systems. In this account we describe our earlier investigations in this field followed by the development of new approaches to the synthesis of polycyclic compounds. Radical ions generated by single-electron transfer (SET) from suitable neutral molecules are used as decisive intermediates in a wide range of interesting cyclization processes and reactions. Various synthetic strategies are presented involving radical anionic or radical cationic species generated by reductive and oxidative PET, respectively.

  • 1 Introduction

  • 2 General Concept

  • 3 Reductive Electron Transfer: Formation of Ketyl and
    γ-Keto Radicals

  • 4 Oxidative Electron Transfer: Formation of α- and β-Keto Radicals

  • 5 Summary

56

Alternatively for the cleavage reactions samarium(II) iodide was used. The a-cyclopropyl ketone 27 gave the same product 28 as in the PET reaction. The reduction was carried out using a 1 mM solution of SmI2 in THF in the presence of 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H)-pyrimidinone (DMPU) as additive.

57

All calculations were carried out using Titan V1 05, Schrödinger Inc., Wavefunction Inc., 2000. For the calculations of the energy profiles of the corresponding 6-endo and 5-exo radicals we used a combination of the B3LYP level and the 6-31G* basis set. The conformational analysis and the transition states were calculated on a semi-empirical level (AM1).

58

Bischof, E. W.; Mattay, J. Abstracts of Papers, XIIIth IUPAC Symposium on Photochemistry, University of Warwick, Coventry, England, 22-28 July, 1990; Royal Society of Chemistry: London, 1990, 85.