Second generation fluorous DEAD reagents have expanded scope in the Mitsunobu reaction and retain convenient separation features.
First generation fluorous DEAD reagent bis(perfluorohexylethyl)azo dicarboxylate (C(6)F(13)(CH(2))(2)O(2)CN=NCO(2)(CH(2))(2)C(6)F(13), F-DEAD-1) has been shown to underperform relative to diisopropylazodicarboxylate in difficult Mitsunobu reactions involving hindered alcohols or less acidic pronucleophiles (phenols). Two new second generation fluorous reagents bearing propylene spacers instead of the ethylene spacers show expanded reaction scope while retaining the easy fluorous separation features. Byproducts from "half fluorous" reagent perfluorooctylpropyl tert-butyl azo dicarboxylate (C(8)F(17)(CH(2))(3)O(2)CN=NCO2(t)Bu, F-DEAD-2) can be removed by fluorous flash chromatography, and byproducts from bis(perfluorohexylpropyl)azo dicarboxylate (C(6)F(13)(CH(2))(3)O(2)CN=NCO(2)(CH(2))(3)C(6)F(13), F-DEAD-3) can be removed by fluorous solid-phase extraction. The new reagents promise to provide general and complementary solutions for separation problems in Mitsunobu reactions without restricting reaction scope.
Dandapani
Sivaraman
S
Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Curran
Dennis P
DP
D001391:Azo Compounds / Q000138:chemical synthesis*; D002851:Chromatography, High Pressure Liquid; D005461:Fluorine / Q000737:chemistry*; D006834:Hydrazines / Q000138:chemical synthesis; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis*; D007202:Indicators and Reagents / Q000737:chemistry; D015394:Molecular Structure; D005466:Fluorocarbons
D001391:Azo Compounds; D005461:Fluorine; D006834:Hydrazines; D006845:Hydrocarbons, Fluorinated; D007202:Indicators and Reagents; C496037:bis(perfluorohexylethyl)azo dicarboxylate; D005466:Fluorocarbons; C496039:bis(perfluorohexylpropyl)azo dicarboxylate; C496035:perfluorooctylpropyl tert-butyl azo dicarboxylate