1360939-70-3Relevant articles and documents
Cobaltocene-induced low-temperature radical coupling reactions in a cobalt-alkyne series
Melikyan, Gagik G.,Rivas, Bianca,Harutyunyan, Stepan,Carlson, Louis,Sepanian, Ruth
, p. 1653 - 1663 (2012/04/23)
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 conversion scheme-from commercial aromatic aldehydes to radical dimers-under nonacidic conditions.
