Preparation of Diester 1. Diisopropylamine (14.6 mL, 104 mmol) was dissolved in 610 mL of THF and the solution cooled to 0 "C. A solution of n-butyllithiumlhexane (38.3 mL of 2.5 M solution, 96 mmol) was added, and the reaction mixture was stirred for 30 min and cooled to -78 "C. Ethyl cyclopropanecarboxylate (18.2 g, 160 mmol) in 30 mL of THF was added dropwise over 15 min, and the resulting solution was stirred for 30 min at -78 "C and allowed to ...