134938-21-9Relevant articles and documents
Nickel- and palladium-catalyzed cross-coupling reactions at the bridgehead of bicyclo[1.1.1]pentane derivatives - A convenient access to liquid crystalline compounds containing bicyclo[1.1.1]pentane moieties
Messner, Matthias,Kozhushkov, Sergei I.,De Meijere, Armin
, p. 1137 - 1155 (2007/10/03)
Radical addition reactions of organyl iodides 7a-s onto [1.1.1]propellane (2) followed by halogen-lithium exchange and transmetallation with zinc chloride, as well as additions of Grignard reagents to 2, have furnished a variety of 3-substituted bicyclo[1.1.1]pentyl-1-magnesium (14) and -zinc (19) derivatives. The latter have been coupled with various alkenyl, aryl, and biaryl halides and triflates under NiCl2dppe, Pd(PPh3)4, or PdCl2(dppf) catalysis to give a number of 1,3-disubstituted bicyclo[1.1.1]pentyl derivatives 17, 20, and 23, several of which exhibit liquid crystalline properties, in moderate to very good yields. The coupling products 20ca, 23ab, 23ae, 23ff, and 23fg have been further transformed to yield bicyclo[1.1.1]pentyl derivatives 32, 24ab, 24ae, 27ff, and 27fg, respectively, bearing alkynyl, cyano, and/or alkenyl groups.
Experimental and Calculated Activation Parameters for Ring Opening of the 1-Bicyclopentyl Radical: The Effect of Bridgehead Substituents
Della, Ernest W.,Pigou, Paul E.,Schiesser, Carl H.,Taylor, Dennis K.
, p. 4659 - 4664 (2007/10/02)
Ring opening of the 1-bicyclopentyl, 3-phenyl-1-bicyclopentyl, and 3-carbomethoxy-1-bicyclopentyl radicals has been studied by experiment and by molecular orbital theory.Our results indicate that the parent system 1a is extremely reluctant to ring open, with an energy barrier of at least 26 kcal mol-1.The ester- and phenyl-substituted radicals rearrange somewhat more readily, with barriers of about 25 and 21 kcal mol-1, respectively.This trend is also observed in the molecular orbital treatment of these processes.Previous reports that include radical rearrangements of this type must now be reconsidered in light of our new data.
