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Paper | Special issue | Vol 74, No. 1, 2007, pp.339-350
Published online, 27th July, 2007
DOI: 10.3987/COM-07-S(W)11
Synthesis of spiro-Annelated Isochromanones by Ring Expansion of Benzocyclobutenones in the Presence of Lithium Diisopropylphosphide

Stefanie C. Kohser, Krishna Gopal Dongol, and Holger Butenschön*

*Institut für Organische Chemie, Universität Hannover, Schneiderberg 1B, D-30167 Hannover, Germany


spiro-Annelated isochromanones are prepared by treatment of benzocyclobutenone with lithium diisopropylphosphide - borane adduct (LDP-BH3), which is easily accessible by metalation of the air stable diisopropylphosphane-borane adduct. The reaction takes place at very mild reaction conditions and involves an oxyanion driven ring opening. As a substituted example the synthesis of the first trifluoromethyl-substituted isochromanone derivative is reported.