201985-09-3Relevant academic research and scientific papers
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.
Cobalt-complexed propargyl cations: Generation under neutral conditions and spontaneous, high-temperature conversion to propargyl Radicals
Melikyan, Gagik G.,Sepanian, Ruth,Spencer, Ryan,Rowe, Aaron,Toure, Pogban
, p. 5541 - 5549 (2010/01/06)
A novel method for the generation of Co2(CO)6- complexed propargyl cations under neutral conditions is developed. The optimized experimental protocol involves treatment of the respective Co 2(CO)6-complexed prop
Cobalt-templated radical processes: Inter- and intramolecular coupling of propargyl radicals
Melikyan, Gagik G.,Deravakian, Asatour,Myer, Steven,Yadegar, Sarkhadoun,Hardcastle, Kenneth I.,Ciurash, Joana,Toure, Pogban
, p. 68 - 75 (2007/10/03)
A novel method for radical C-C bond formation in the α-position to Co2(CO)6-clusters has been elaborated. The two-dimensional exploration of the process resulted in the discovery of structurally diverse O- and S-containing organic molecules capable of acting as efficient mediators in reductive coupling reactions, and in the elaboration of the preparative synthesis of 3,4-disubstituted 1,5-alkadiynes and carbocycles with eight- and nine-membered rings.
