For synthesis of drugs see www.drugsyn.org/search.htm

Distilling over sodium hydride is not advisable as it will react with diisopropylamine to form its sodium salt.

Dear Leonardo, Unlike our collegue Rajesh stated, you CAN distill diisopropylamine from NaH or Na, under nitrogen as reported in Armarego and Chai´s "Purification of Laboratory Chemicals". See the procedure bellow:

Diisopropylamine [ 108- 18-91 M 101.2, b 83.5°/760mm, n 1.39236, d 0.720, pK25 11.20.

Distd from NaOH, or refluxed over Na wire or NaH for three minutes and distd into a dry receiver under N2.

Simple refluxing and distilling from NaOH gives you suitable DIPA to prepare LDA.

You can distill DIPA over CaH2 under Ar or N2.

Better use CaH2

WE CAN USE KOH

Refluxing and without vacuum distilling from NaOH gives you suitable DIPA to prepare LDA.