Cobaltocene-Induced Low-Temperature Radical Coupling Reactions in a Cobalt–Alkyne Series

Autor:	Stepan Harutyunyan, Louis Carlson, Bianca Rivas, Gagik G. Melikyan, Ruth Sepanian
Rok vydání:	2012
Předmět:	chemistry.chemical_classification Steric effects Radical Organic Chemistry Cationic polymerization Alkyne Photochemistry Medicinal chemistry Coupling reaction Inorganic Chemistry chemistry.chemical_compound chemistry Intramolecular force Propargyl Cobaltocene Physical and Theoretical Chemistry
Zdroj:	Organometallics. 31:1653-1663
ISSN:	1520-6041 0276-7333
DOI:	10.1021/om2006497
Popis:	A novel method for the low-temperature generation of Co2(CO)6-complexed propargyl radicals is developed. It consists of an in situ preparation of the respective cationic species (−50 to −10 °C) and their rapid reduction with cobaltocene, Cp2Co, at −50 °C. The optimized experimental protocol is applied to both inter- and intramolecular reactions, affording topologically diverse α-aryl and α-napthyl, d,l- and meso-1,5-hexadiynes and 1,5-cyclodecadiynes. The d,l configuration is the most preferable steric arrangement in intermolecular radical C–C bond-forming reactions (d,l 69–92%), while a reversal of stereoselectivity is observed in intramolecular cyclizations (meso 79%). Under oxidizing conditions (Ce4+), decomplexation affords d,l-3,4-diaryl- and d,l-3,4-(1-/2-naphthyl)-1,5-hexadiynes in good to excellent yields (47–98%). An enhanced functional tolerance is showcased by introducing peripheral acid-sensitive functionalities, such as benzyloxy and methylenedioxy groups, and carrying out a five-step convers...
Databáze:	OpenAIRE
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