71032-66-1Relevant articles and documents
Dihalocarbene insertion reactions into C-H bonds of compounds containing small rings: Mechanisms and regio- and stereoselectivities
Brinker, Udo H.,Lin, Guoying,Xu, Linxiao,Smith, William B.,Mieusset, Jean-Luc
, p. 8434 - 8451 (2008/02/13)
(Chemical Equation Presented) Novel insertion reactions of dichloro- and dibromocarbene into carbon-hydrogen bonds adjacent to cyclopropane rings are reported. It is found that the predominant isomers formed in the reactions with bicyclo[4.1.0]heptane result from insertion into the endo carbon-hydrogen bonds alpha to the three-membered ring. In the reactions of bicyclo[3.1.0]hexane, however, the exo dihalocarbene insertion products are formed as the major isomers. In some compounds cyclopropane rings "activate" adjacent carbon-hydrogen bonds, whereas other systems containing three-membered rings do not. Moreover, the influence of various substituents (methyl, geminal dimethyl, phenyl, methoxy, and ethoxy) attached to bicyclo-[3.1.0]hexane and bicyclo[4.1.0]heptane in dihalocarbene reactions has been studied. The findings can be explained by the concept of maximum orbital overlaps of Walsh orbitals of the cyclopropane rings and the α carbon-hydrogen bonds. In stark contrast, selective insertion into the tertiary carbon-hydrogen bonds of the cyclobutane ring in bicyclo[4.2.0]octane is observed.
PHOTOCHEMISTRY OF ALKYL HALIDES - VII. CYCLOPROPANATION OF ALKENES
Kropp, Paul J.,Pienta, Norbert J.,Sawyer, Joy A.,Polniaszek, Richard P.
, p. 3229 - 3236 (2007/10/02)
The previously observed cyclopropanation of alkenes by irradiation of diiodomethane (1) in their presence has been studied in more detail and found to be a synthetically useful procedure which is significantly less subject to steric effects than the traditional Simmons-Smith method.The results from photocyclopropanation of a variety of alkenes are summarized in Tables 1 and 3-4.In a number of cases the photochemical procedure afforded improved results over the Simmons-Smith method, particularly with sterically congested alkenes.Cycloalkenes showed relative rates of photocyclopropanation as a function of ring size similar to those of the Simmons-Smith method (Table 5).However, the photocyclopropanation reaction exhibited steadily increasing relative rates with increasing substitution about the double bond-in contrast with the Simmons-Smith method (Table 6), in which steric effects offset increasing nucleophilicity of the alkene with increasing substitution.The α-iodocation 2 is suggested as the methylene transfer species.In the presence of lithium bromide cation 2 was trapped to afford bromoiodomethane.
