BICYCLO[2.1.0]PENTANE的合成.pdfVIP

Organic Syntheses, Coll. Vol. 5, p.96 (1973); Vol. 49, p.1 (1969). BICYCLO[2.1.0]PENTANE 1 Submitted by P. G. Gassman and K. T. Mansfield . Checked by G. N. Taylor and K. B. Wiberg. 1. Procedure A. Diethyl 2,3-diazabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate . In a 1-l., three-necked, round- bottomed flask equipped with a constant-pressure dropping funnel, a mechanical stirrer, and a reflux condenser is placed 174 g. (1.0 mole) of ethyl azodicarboxylate2 in 150 ml. of ether. Freshly prepared cyclopentadiene3 (70 g., 1.06 moles) is added dropwise over a 1-hour period to the stirred ethereal solution of diethyl azodicarboxylate. During the addition a gentle reflux is maintained by external cooling with an ice-water bath as needed. When the addition is complete, the reaction mixture is allowed to stand for 4 hours, or less if the yellow color of the azodicarboxylic acid ester disappears. The dropping funnel and condenser are replaced by a glass stopper and a short distillation head, respectively. The ether and unreacted diene are distilled off on a steam bath and the residue is transferred to a 500-ml. round-bottomed boiling flask equipped with a 30-cm. Vigreux column. After a small forerun the diethyl 2,3-diazabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate distills to give 218–228 g. (91–95%) of a colorless or very pale yellow, viscous liquid, b.p. 119–120° (0.4 mm.). B. Diethyl 2,3-diazabicyclo[2.2.1]heptane-2,3-dicarboxylate . A mixture of 112 g. (0.47 mole) of diethyl 2,3-diazabicyclo[2.2.1] hept-5-ene-2,3-dicarboxylate and 125 ml. of absolute ethanol is placed in a standard Paar bottle along with 0.2 g. of