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Paper | Special issue | Vol 77, No. 2, 2009, pp.991-1005
Published online, 29th September, 2008
DOI: 10.3987/COM-08-S(F)85
Selective Lithiation of 4- and 5-Halophthalans

Daniel García, Francisco Foubelo,* and Miguel Yus*

*Department of Organic Chemistry, Faculty of Sciences and Institute of Organic Synthesis (ISO), University of Alicante, P.O. Box 99, 03080 Alicante, Spain

Abstract

The reaction of 4- and 5-halophthalans 5 with lithium and a catalytic amount of DTBB at -78 °C leads to the formation of the corresponding functionalized organolithium intermediates 6 and 11, which by reaction with carbonyl compounds give, after hydrolysis, the expected substituted phthalans 8 and 13, respectively. When after reaction with the carbonyl compound the system is allowed to react at 0 °C, a second lithiation occur: A reductive opening of the heterocycle takes place with some regioselectivity leading to new organolithium intermediates 9 and 14/15 that by reaction with electrophiles lead, after hydrolysis, to polyfunctionalized molecules 10 and 16/17, respectively.