Preparation of Aldimines and Ketimines

Apparatus for reaction (1) 1-1, round-bottomed, three-necked flask, equipped with a dropping funnel, a mechanical stirrer and a thermometer-outlet combination for reaction (2) 1-1, round-bottomed flask and reflux condenser connected to a Dean-Stark water separator. 

The imines decompose upon standing at room temperature, but can be kept unchanged at — 20 °C for a few weeks under inert gas in well-closed bottles. It is advisable, however, to use the freshly redistilled imines for syntheses. The redistillations usually give a forerun, mainly consisting of t-butylamine, and a higher-boiling residue (compare Ref. [2]). 

Cyclohexylamine (1.2 mol, 118.8g), cyclopentanone (l.Omol, 84.0g), or cyclohexanone (1.0 mol, 98.0g) and benzene (125ml) are placed in the flask. The mixture is heated under reflux for 6 h. Almost the stoichiometrical amount of water is collected. Most of the benzene is then removed under reduced pressure (rotary evaporator) after which the products are isolated by distillation through a 30-cm Vigreus column. The imines, b.p. 108 C/12 mmHg, nD(20) 1.4946 and b.p. 125 °C/12 mmHg (solidifying at 20 °C), respectively are obtained in 90% yields. 

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