Syntheses with organoboranes.: XIII.: Synthesis of (ω-(4-bromophenyl)alkanoic acids and their borylation

omega-(4-Bromophenyl)alkanoic acids 2c-e were obtained from 1-bromo-4-alkenylbenzenes 5c-e by hydroboration-thermal isomerization-oxidation. Their esters 11c-e were transformed in good yields into the corresponding boronates 12c-e by the cross-coupling reaction with 4,4,5,5,4',4',5',5'-octamethyl[2,2']bi[[1,3,2]dioxaborolanyl] (10) in an ionic liquid, [bmim][BF4]. The use of pinacolborane for the coupling reaction in the ionic liquid gave debromination products, and low yields of 12c-e. Ethyl 3-(4-bromophenyl)propanoate (7c) was transformed into ethyl 3-(4-[1,3,2]dioxaborolanyl)propanoate (9c) by the cross-coupling with [2,2']bi[[1,3,2]dioxaborinanyl]. (C) 2002 Elsevier Science B.V. All rights reserved.