2-Diazo-3-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-3-butenoic Acid, Methyl Ester

Abstract

[166392-81-0] C11H20N2O3Si (MW 256) InChI = 1S/C11H20N2O3Si/c1-8(9(13-12)10(14)15-5)16-17(6,7)11(2,3)4/h1H2,2-7H3 InChIKey = XLIWNMXKBCISIR-UHFFFAOYSA-N (precursor to highly chemoselective metal carbenoid) Physical Data: IR (neat) 2950, 2107, 1714, 1669, 1466, 1352 cm−1; 1H NMR (CDCl3) δ 4.98 (d, J = 1.8 Hz, 1H), 4.23 (d, J = 1.8 Hz, 1H), 3.78 (s, 3H), 0.90 (s, 9H), 0.21 (s, 6H). Solubility: soluble in most organic solvents including hydrocarbons. Form Supplied in: not commercially available. Preparative Methods: 1 triethylamine (2 mL, 14.3 mmol) was added to a stirring solution of methyl 2-diazo-3-oxobutanoate (3.1 g, 10.1 mmol) in dichloromethane (26 mL) at 0 °C under an inert argon atmosphere. tert-Butyldimethylsilyl trifluoromethanesulfonate (2.8 mL, 12.2 mmol) was added over 5 min and the mixture was further stirred for 30 min at 0 °C. The reaction mixture was diluted with hexane (100 mL), and the organic phase was subsequently washed with dilute aqueous sodium bicarbonate (100 mL) and brine (100 mL). The organic layer was dried (MgSO4), and the solvent was removed under reduced pressure to yield the title product as an orange oil (essentially quantitative yield), which was used without further purification. Purification: the title compound can be used without further purification, but usually it contains a trace amount of bis(tert-butyldimethylsilyl) ether as a major impurity. The compound can be quickly purified by flash chromatography in silica gel with hexane containing 1% triethylamine. Handling, Storage, and Precautions: the title compound is labile under acidic conditions. Unlike other vinyldiazoacetates, which slowly undergo electrocyclization to form pyrazoles, this diazo compound is thermally stable and can be stored in a refrigerator for several months without significant decomposition. As with all diazo compounds, caution should be emphasized in handling this compound, and excessive heating should be avoided. As a precaution, it is recommended that all procedures using this compound should be conducted behind a blast shield.