Vicinal Stereocontrol During Nucleophilic Addition to Arene Chromium Tricarbonyl Complexes: Formal Synthesis of (.+‐.)‐erythro Juvabione.

Abstract

All reactions involving chromium tricarbonyl complexes were performed using oven-dried (125 ºC) glassware under anhydrous, oxygen free argon atmosphere. All reactions were performed in freshly distilled (under nitrogen) solvents and monitored by TLC on silica gel. The TLC plates were visualized with UV light and/or with phosphomolybdic acid solution in ethanol. Reactions performed at -60 ºC were maintained at that temperature using ethanol bath and Neslab Cryotrol. Flash chromatography was performed on silica gel with mesh 170-400 under nitrogen pressure. NMR spectra were recorded on a Varian Gemini 200 (200 MHz) or Varian Gemini 300 (300 MHz) or Varian 600 (600 MHz) spectrometer. FTIR spectra were recorded as neat oils or KBr pellet on a Nicolet Impact 400 FTIR spectrometer. High resolution mass spectra (HRMS) of compounds were recorded in-house using a Kratos MS25A instrument by either EI (Electron Ionization) or FAB (Fast Ion Bombardment). Capillary GC was carried out using HP5890 Series II Gas Chromatograph. The melting points were measured on a Thomas Hoover apparatus and are uncorrected. The purity of new compounds was assessed from their 1 H and 13 C NMR spectra. 4-Methoxy trimethylsilylbenzene was prepared by the literature procedure. 1 Chromium complexes are previously reported in the literature and were prepared from the corresponding arenes by Pauson and Mahaffy procedure of refluxing the arene with chromium hexacarbonyl in dibutyl ether and THF mixture. 2 endo-2-Naphthyl isoborneol was prepared from D(+) Camphor by addition of naphthylmagnesium bromide in THF in the presence of anhydrous cerium chloride. 3 S2 Experimental parameters for Capillary GC on HP5890 Series II Gas Chromatograph: Column: 25 m HP 5MS capillary column Carrier gas: Helium at 45 psi Injector temperature: 200 ºC Detector temperature: 300 ºC Run time: 26 minutes η 6 -(4-methoxytrimethylsilylbenzene)chromium tricarbonyl (3)