Formaldehyde Dimethylhydrazone

Introduction of a hydrazine-moiety¹⁾: To a cooled (0 °C) solution of 3-methyl-2-cyclopentenone (2 mmol) in dry ether (10 mL) is added dropwise TDS triflate (2.5 mmol) followed by a solution of Formaldehyde dimethylhydrazone (0.34 mL, 4 mmol) in dry ether (4 mL) over 10 min under an argon atmosphere. The mixture is stirred for 15 min, quenched with TBAF (1 M in THF, 2.5 mL) and the mixture is diluted with Et₂O (20 mL) and washed with brine. The combined organic layer is concentrated, and the residue is purified by column chromatography (1:1 Et₂O-petroleum ether) to give the product 3 (306 mg, 91%) as an oil.