OLIGOMERIC 1,2-DIHYDRO-1-MAGNESACYCLOBUTA[a]NAPHTHALENE

Abstract

l,2-Dihydro-l-magnesacyclobuta[a]naphthalene (4), a mixed benzylic/aromatic diorganylmagnesium reagent, was prepared from the corresponding dihalide and magnesium in THF, followed by removal of MgBrCl with 1,4-dioxane. It is the first example of its kind which is soluble in THF and was shown (UV, NMR, degree of association) to establish an equilibrium between a highly polar oligomer 4a and a less highly associated and more conventional diorganylmagnesium 4b. 121Brought to you by | Purdue University Libraries Authenticated Download Date | 5/27/15 6:22 AM Friedrich Bickelhaupt et al. Oligomeric 1,2-Hydro-1 -Magnesacyclobuta[a]Naphthalene EXPERIMENTAL GeneralAll manipulations involving organometallic compounds were carried out in fully sealed glassware using standard high vacuum techniques. Solvents were dried by distillation from liquid Na/K alloy after predrying on NaOH. Magnesium was sublimed twice before use. 1 -Bromo-2-methylnaphthalene (Aldrich) and Λ'-bromosuccinimide (NBS, from ACROS) were commercially available. NMR spectra were measured on a Bruker AC 200 spectrometer ('H NMR: 200 MHz; 13 C NMR: 50.3 MHz) and on a Bruker MSL 400 spectrometer ('H NMR: 400.1 MHz; 13 C NMR: 100.6 MHz); the assignments are based on NOE difference and 2D measurements. GCMS analyses were performed on a HP 5890 GC/ 5970 MS combination, operating at 70 eV and equipped with a Chrompack BP1 (QSGE) 50 mJ 0.25 mm column. HRMS measurements were performed on a Finnigan MAT 90 mass spectrometer under EI conditions. UV/VIS spectra were recorded on a Beckman DU-64 spectrophotometer. l-Bromo-2-chloromethylnaphthalene (5) The synthesis of 5 was performed in analogy to that reported for 2a [11]. l-Bromo-2bromomethylnaphthalene was prepared by light induced radical bromination of l-bromo-2methylnaphthalene with 1.