Enantioselective cyclopropanation of carboxylic esters with alkyl magnesium bromides in the presence of titanium(IV) (4R,5R)-TADDOLates

Autor:	Oleg G. Kulinkovich, Yulia A. Konik, Dzmitry G. Kananovich
Rok vydání:	2013
Předmět:	chemistry.chemical_classification Chemistry Cyclopropanation Organic Chemistry Enantioselective synthesis Ether Biochemistry Catalysis chemistry.chemical_compound Yield (chemistry) Drug Discovery Propionate Organic chemistry Diethyl ether Isopropyl
Zdroj:	Tetrahedron. 69:6673-6678
ISSN:	0040-4020
DOI:	10.1016/j.tet.2013.05.118
Popis:	The reaction of isopropyl 4-chlorobutyrate with 3 equiv of n-BuMgBr in the presence of 1 equiv of titanium(IV) (4R,5R)-TADDOLate in diethyl ether led to the formation of (1S,2S)-(3-chloropropyl)-2-ethylcyclopropanol in 55–70% yield and 55–65% ee. The reaction was performed in the presence of 20 mol % of the catalyst without significant loss in yield and enantioselectivity when solutions of the carboxylic ester and the Grignard reagent were added simultaneously at an equal rate to a refluxing solution of the titanium catalyst in ether. The cyclopropanation of isopropyl propionate under the same conditions gave (1S,2S)-1-ethyl-2-propylcyclopropanol in 50% yield and 65% ee. Its absolute configuration was determined by chemical correlation through acid-catalyzed isomerization to enantiomerically enriched (R)-(−)-4-methyl-3-heptanone, known as a minor component of the trail pheromone of ant Aphaenogaster albisetosus and enantiomer of the alarm pheromone of leaf-cutting ants Atta texana.
Databáze:	OpenAIRE
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