β‐Silyl Arenes in the Arene—Olefin Photocyclization Reaction.

Abstract

Organo-silicon compounds S 0060β-Silyl Arenes in the Arene-Olefin Photocyclization Reaction. -Benzyltrimethylsilane undergoes intermolecular arene-olefin photocyclization with cycloalkenes to give predominantly single products, even with problematical cyclohexene and cis-cyclooctene. The presence of a β-silyl group has a powerful stabilization effect on the electron-deficient early transition state. It thus allows the reactions to be run to complete consumption of the starting arene without significant polymer formation. -(DELONG*, M. A.; MATHEWS, J. A.; COHEN, S. L.; GUDMUNDSDOETTIR, A.; Synthesis 2007, 15, 2343-2350; Dep. Chem., Univ., Cincinnati, OH 45221, USA; Eng.) -Bartels

Formation of a Three‐Membered Ring

“…The b-silyl effect has been found to be operative in excited states, where this group exerts a remarkable effect on the yield and selectivity of intermolecular [3 þ 2] cycloaddition (Scheme 4.53) [80]. Although cyclohexene and cis-cyclooctene each produce poor yields and poor selectivities with substrates such as toluene and anisole, this reaction is capable of producing intermolecular [3 þ 2] cycloadducts with a few cycloalkenes.…”