2,7-Di-tert-butyl-9-fluorenylmethyl Chloro-formate

Abstract

[287381-46-8] C23H27ClO2 (MW 370.92) InChI = 1S/C23H27ClO2/c1-22(2,3)14-7-9-16-17-10-8-15(23(4,5)6)12-19(17)20(18(16)11-14)13-26-21(24)25/h7-12,20H,13H2,1-6H3 InChIKey = PHUMWWRUIGKGNN-UHFFFAOYSA-N (base-labile protecting group for primary and secondary amines with the resulting carbamates having improved solubility in organic solvents over those of the Fmoc protecting group) Alternate Name: 2,7-di-tert-butyl-9-fluorenylmethoxycarbonyl chloride; carbonochloridic acid, [2,7-bis(1,1-dimethylethyl)-9H-fluoren-9-yl]methyl ester; Fmoc*-Cl. Physical Data: mp 63–65 °C. Solubility: soluble in organics (CH2Cl2, CHCl3, pentane, etc.); reacts with alcohols, amines, and water. Form Supplied in: 2,7-di-tert-butyl-9-fluorenylmethanol chloroformate and its immediate synthetic precursor (2,7-di-tert-butyl-9-fluorenylmethanol) are available from Aldrich, with the immediate synthetic precursor priced considerably more economically. Analysis of Reagent Purity: 1H NMR, IR, elemental analysis. Preparative Methods: the title reagent can be prepared in three steps from fluorene1 by Friedel-Crafts alkylation with (CH3)3 CCl and FeCl3 to give 2,7-di-tert-butyl-9-fluorene, hydroxymethylation with n-BuLi and paraformaldehyde to give 2,7-di-tert-butyl-9-fluorenylmethanol, and conversion to the chloroformate with phosgene. Purification: low-temperature (−78 °C) recrystallization from pentane. Handling, Storage, and Precautions: treat with precautions typical of nonvolatile acid chlorides and chloroformates—avoid skin and eye contact; avoid breathing fumes, which may contain HCl, by working in a fume hood; open bottles carefully, as pressure may develop; protect from moisture; reactions with nucleophiles, such as amines, may be exothermic and should be performed with adequate dilution and cooling.