The nitrogen-centred radical generated by reaction of an N-phosphoramidate or N-cyanamide, attached to a tri- or tetramethylene tether extended from the C-1 of a carbohydrate, with (diacetoxyiodo)benzene (DIB) and iodine can undergo a regio- and stereoselective intramolecularhydrogenatomtransfer (HAT) reaction to furnish four different oxa-azaspirobicyclic systems: 1-oxa-6-azaspiro[4.4]nonane, 1-oxa-6-azaspiro[4
Intramolecular 1,5- versus 1,6-Hydrogen Abstraction Reaction Promoted by Alkoxy Radicals in Carbohydrate Models
作者:Cosme G. Francisco、Raimundo Freire、Antonio J. Herrera、Inés Peréz-Martín、Ernesto Suárez
DOI:10.1021/ol025981u
日期:2002.5.1
[GRAPHICS]The alkoxy radical generated by reaction of 3,7-anhydro-2-deoxyoctitols with (diacetoxyiodo)benzene (DIB) and iodine abstracts regioselectively either the proton at C7 or that at C4 depending on the electronegativity of the substituent at C4. The correct election of this substituent can switch the reaction to give 2,9-dioxabicyclo[3.3.1]nonane or hexahydro-2H-furo[3,2-b]pyran ring systems.