65108-25-0Relevant academic research and scientific papers
Regio- and Stereo-selective Formation of Methylenecyclopropane Complexes from Allenes and Benzylidenepentacarbonyl Tungsten
Fischer, Helmut,Bidell, Wolfgang,Hofmann, Josef
, p. 858 - 859 (1990)
Benzylidenepentacarbonyl tungsten reacts with dimethylallene and phenylallene, respectively, by regiospecific and stereoselective transfer of the benzylidene group to the allene and co-ordination of the product methylenecyclopropane which can be cleaved almost quantitatively from the metal by Br(-); the structure of the 2-phenyl-3,3-dimethylmethylenecyclopropane complex is established by an X-ray structure analysis.
Methylenecyclopropane Rearrangement as a Probe for Free Radical Substituent Effects. σ·Values for Potent Radical-Stabilizing Nitrogen-Containing Substituents
Creary, Xavier,Engel, Paul S.,Kavaluskas, Natasha,Pan, Li,Wolf, Allison
, p. 5634 - 5643 (2007/10/03)
A series of nitrogen-containing 2-aryl-3,3-dimethylmethylenecyclopropanes have been prepared and rearrangement rates to the corresponding 2-arylisopropylidenecyclopropanes have been measured. These rates are dependent on the nature of the nitrogen-containing group in the para-position of the aryl group. Rearrangement rates have been used to calculate σ· values, which are a measure of the radical stabilizing ability of the substituent. Groups such as p-N=N-Bu-t, p-CH=N-Bu-t, p-NH2, p-CH=N-OH, and p-CH=N-OCH3, are "good" radical stabilizers. We have also classified groups such as p-CH=N-NMe2, p-N=N-Ph, p-N=N(O)-Bu-t, p-CH=N(O)-Bu-t, and p-CH=N-O- M+, which have an extraordinarily large radical stabilizing effect, as "Super Stabilizers". These substituents stabilize the transition state of the methylenecyclopropane rearrangement by extensive spin delocalization. In the case of the latter three substituents, nitroxyl type stabilization is proposed. Density functional calculations (B3LYP/6-31G*) have been carried out on a series of nitrogen-containing substituted benzylic radicals. Rates of the methylenecyclopropane rearrangement correlate with radical stabilization energies (ΔE) determined from an isodesmic reaction of substituted benzylic radicals with toluene. These calculations confirm substantial spin delocalization onto the nitrogen-containing substituents on the para-position of the benzylic radical.
THE PYRIDINE N-OXIDE GROUP. A POTENT RADICAL STABILIZING FUNCTION
Creary, Xavier,Mehrsheikh-Mohammadi, M. E.
, p. 749 - 752 (2007/10/02)
The rate of the methylenecyclopropane rearrangement is greatly enhanced by the 4-pyridyl N-oxide group due to spin delocalization in the transition state which imparts nitroxide radical character to the biradical intermediate.
Regioselectivity in the Addition of Singlet and Triplet Carbenes to 1,1-Dimethylallene. A Probe for Carbene Multiplicity
Creary, Xavier
, p. 1611 - 1618 (2007/10/02)
Singlet carbenes add preferentially to the more substituted bond of 1,1-dimethylallene (1), to give methylenecyclopropanes 3 as the major product.In contrast, many triplet carbenes add with differing regioselectivity, giving the thermodynamically preferre
