477952-41-3Relevant academic research and scientific papers
Enantioselective alkene radical cations reactions
Crich, David,Shirai, Michio,Brebion, Franck,Rumthao, Sochanchingwung
, p. 6501 - 6518 (2007/10/03)
The reaction of enantiomerically enriched 2-methyl-2-nitro-3-(diphenylphosphatoxy)alkyl radicals with tributyltin hydride and AIBN in benzene at reflux results in the formation of alkene radical cation/anion pairs, which are trapped intramolecularly by am
Stereochemical memory effects in alkene radical cation/anion contact ion pairs: Effect of substituents, and models for diastereoselectivity
Crich, David,Ranganathan, Krishnakumar
, p. 9924 - 9929 (2007/10/03)
A series of 12 stereochemically defined 2,m-dimethyl- and 2,m,n-trimethyl-6-benzylamino-2-nitro-3-(diphenylphosphatoxy)hexanes have been synthesized and their cyclization reactions leading to di- and trisubstituted N-benzyl pyrrolidines examined in the presence of tributyltin hydride and azoisobutyronitrile in benzene at reflux. The cyclizations are interpreted in terms of generation of an alkyl radical by abstraction of the nitro group with a stannyl radical. The phosphate leaving group is then expelled in a heterolytic cleavage to give a contact alkene radical cation/phosphate anion pair. For the majority of the examples studied, the cyclizations are best understood in terms of nucleophilic attack by the amine on the opposite face of the alkene radical cation to the one shielded by the leaving group, within the confines of the initial contact ion pair, resulting in overall cyclization with inversion of configuration. Dependent on the relative stereochemistry of the substituents, the cyclization is envisaged as taking place through either chair-like or twist-boat-like transition states with the maximum number of substituents pseudo-equatorial. The model breaks down when cyclization on the initial contact ion pair would engender significant destabilizing steric interactions, especially 1,3A strain in the alkene radical cation. In these cases a fully equilibrated Beckwith-Houk-type transition state provides a satisfactory model. Interesting examples of matching and mismatching in the Corey-type oxazaborolidine-mediated reduction of alkyl (methyl-1-nitroethyl) ketones by a β-methyl group in the alkyl chain are reported, and the mismatching is attributed to a developing syn-pentane interaction in the transition state.
Enantioselective cyclization of alkene radical cations
Crich, David,Shirai, Michio,Rumthao, Sochanchingwung
, p. 3767 - 3769 (2007/10/03)
(Matrix Presented) Enantiomerically enriched β-(diphenylphosphatoxy) nitroalkanes undergo radical ionic fragmentation, induced by tributyltin hydride and AIBN in benzene at reflux, to give alkene radical cations in contact radical ion pairs. These contact
Diastereoselectivity in the cyclization of alkene radical cations generated under non-oxidizing conditions: Contact ion pairs and memory effects
Crich, David,Ranganathan, Krishnakumar
, p. 12422 - 12423 (2007/10/03)
A series of highly diastereomerically enriched 1,5-dimethyl-, 2,5-dimethyl-, and 3,5-dimethyl-N-benzyl-5-nitro-4-(diphenylphosphatoxy)hexylamines were exposed to tributyltin hydride and AIBN in benzene at reflux. The ensuing reactions, interpreted in term
