DIRECTED LITHIATION OF CHLOROBENZENES - REGIOSELECTIVITY AND APPLICATION TO A SHORT SYNTHESIS OF BENZOCYCLOBUTENES

Chlorobenzene and its OMe, OSiMe2-£-Bu, and Cl derivatives 1 were lithiated with high regioselectivity ortho to chlorine by treatment with sec-BuLi in THF at -105 °C without complications due to benzyne formation. The lithio species thus generated underwent smooth Michael addition on treatment with l-(phenylsulfonyl)-l-(trimethylsilyl)ethene (2). The desilylated Michael adducts 3 or 6 were converted in good yields to l-(phe-nylsulfonyl)benzocyclobutenes 7 via benzyne intermediates. © 1990, American Chemical Society. All rights reserved.