[58419-23-1] · C13H22CuLiO2 · Lithium (3,3-Diethoxy-1-propen-2-yl)(3,3-dimethyl-1-butynyl)cuprate · (MW 280.84)
(mixed organocuprate; acrolein and acrylate equivalent)
Preparative Methods: prepared in situ from 3,3-Dimethyl-1-butynylcopper(I) and 2-Lithio-3,3-diethoxy-1-propene at -78 °C; ether or a mixture of ether/THF can be used as solvent.
Handling, Storage, and Precautions: air- and moisture-sensitive; use in a fume hood.
Lithium (3,3-diethoxy-1-propen-2-yl)(3,3-dimethyl-1-butynyl)cuprate (1) has been used primarily as an a-acrolein and a-acrylate anion equivalent (eq 1). The t-butyl acetylide ligand has proven to be superior over other typical mixed cuprate ligands due to improved solubility, increased thermal stability, and higher yields. The 3,3-diethoxypropenyl unit is cleanly transferred in 1,4-additions to enones (eq 2), though the reaction was reported to be slower and the yields moderate when b-substituents of increasing bulk were introduced.1,2 The addition of (1) to cyclic g-hydroxy enones provides useful intermediates for the synthesis of a-methylene-g-lactones (eq 3).2 The reagent will not react with primary or vinyl halides but will add to allylic halides in excellent yield (eq 4).2
The addition of (1) to cyclic allylic epoxides was shown to give predominantly 1,2-addition vs. 1,4-addition.3 Maximum yields were obtained at -40 °C, giving exclusively trans addition products (eq 5). Hydrolysis of acetals (8) and (9) was followed by oxidation to give the mixture of acids (10) and (11). If this mixture was treated with 1,3-Dicyclohexylcarbodiimide (conditions a), only the acid with the proximal hydroxy group
cyclized to give trans-a-methylenelactone (12). When the mixture of (10) and (11) was refluxed in benzene in the presence of p-Toluenesulfonic Acid (conditions b), (12) was isolated along with the cis-a-methylenelactone (13).
Matthew E. Voss
The Du Pont Merck Pharmaceutical Company, Wilmington, DE, USA