[-] · C12H26CuLiSi2 · Lithium Bis(3-trimethylsilyl-1-propen-2-yl)cuprate · (MW 297.05)
(precursor to diene used in tandem Diels-Alder reactions)
Preparative Method: 2-Bromo-3-trimethylsilyl-1-propene is lithiated with n-Butyllithium in ether at -78 °C, followed by addition of 0.5 equiv Copper(I) Iodide1.
Handling, Storage, and Precautions: air- and moisture-sensitive; use in a fume hood.
Lithium bis(3-trimethylsilyl-1-propen-2-yl)cuprate (1) has been used to prepare 2,3-[bis(trimethylsilyl)methyl]-1,3-butadiene (2) via an oxidative dimerization reaction promoted by Copper(II) Chloride (eq 1). Reaction of (2) with Dimethyl Acetylenedicarboxylate afforded the cyclohexadiene (3) in 82% yield. Oxidative bis-desilylation of (3) and reaction with N-Phenylmaleimide provided the linear tricycle (4) in moderate yield (eq 2). Additional examples of the tandem Diels-Alder sequence with a variety of dienophiles are also given.1
Matthew E. Voss
The Du Pont Merck Pharmaceutical Company, Wilmington, DE, USA