On the Use of N-amino Ethers as Capped Azomethine Ylide Equivalents

Article abstract of DOI:10.1021/jo00378a013

N-<(Trimethylsilyl)methyl>amino ethers have been found to act as azomethine ylide equivalents.Treatment of these compounds with lithium fluoride in the presence of a reactive dipolarophile afforded dipolar cycloadducts in high yield.The cycloaddition proceeded with complete stereospecificity with dimethyl fumarate and maleate.This result is consistent with the intermediacy of an azomethine ylide.The reaction of N-benzyl-N-(methoxymethyl)-N-<(trimethylsilyl)methyl>amine afforded several silylated diamines when treated with zinc chloride or cesium fluoride in the absence of trapping agent.This can be attributed to an initial loss of the methoxy group to give a transient iminium ion.This species reacts further with the azomethine ylide or undergoes hydrolysis to give a silylated amine.The cycloaddition behavior of several unsymmetrically substituted azomethine ylide precursors was also examined.Competitive rate studies showed that the cycloaddition is compatible with a HOMO-controlled process.The regiochemistry of the cycloaddition, however, is not easily rationalized by simple FMO considerations and may instead be related to the charge transfer interaction energy of the reaction.