Zn(OTf)2 catalyzed addition–cyclization reaction of allenylphosphine oxides with propargyl alcohol-unexpected formation of 2,5-dimethylenetetrahydrofurans and 2-substituted furans
摘要:
A novel synthesis of 2,5-dimethylenetetrahydrofurans, 2-substituted furans and a beta,omega-diketophosphonate in good to excellent yields has been achieved by the reaction of allenylphosphine oxides/allenylphosphonate with propargyl alcohol using zinc triflate/triethylamine combination. (C) 2011 Elsevier Ltd. All rights reserved.
time. This protocol, merging visiblelight photoredox and palladium catalysis, provides a direct approach to conjugated tertiary allylic alcohol derivatives with broad functional group tolerance in moderate to excellent yields. Mechanistic studies suggest that, although two possible pathways exist in the transformation, radical oxyalkenylation promoted by visiblelight photoredox takes over the major
A variety of 4-phosphinylpyrrolidin-3-ones was prepared via a [3+2] cycloaddition between aryl aldonitrones and phosphinylallenes. The products were isolated as unique 4,5-trans diastereomers, in yields between 47% and 80%, over 23 examples. In the case of chiral racemic allenes, a 2:1 to 4:1 moderate 2,5-diastereoselectivity was observed. Under the reaction conditions, the cycloadducts directly undergo