Benzyl(methoxymethyl)((trimethylsilyl)methyl)amine

UsesN-(Methoxymethyl)-N-(trimethylsilylmethyl)benzylamine is useful reagent in synthesizing N-benzyl substituted pyrrolidines by [3+2] cycloaddition to α,ßunsaturated esters.

UsesN-Benzyl-N-(methoxymethyl)- N-trimethylsilylmethylamine (1) is a valuable reagent for in situ generation of the N-benzyl azomethine ylide (2). It is generally preferred over alternative silylmethylamine precursors6–8 because of ease of handling and use. The ylide (2) is most conveniently generated from (1) using a catalytic amount of trifluoroacetic acid as described by Achiwa.Alternative catalysts include LiF, TBAF,Me3SiOTf–CsF, or Me3SiI–CsF. Mechanistic studies provide evidence that the reactive intermediate generated from (1) with either CF3CO2H or F is a 1,3-dipolar species. Reaction of (2) with alkenes provides an efficient convergent route to pyrrolidine derivatives. Alkynes afford 3-pyrrolines which can be converted into pyrroles.The ylide (2) reacts most readily with electron deficient alkenes and alkynes since this pairing results in a narrow dipole HOMO–dipolarophile LUMO energy gap.Examples of suitable dipolarophiles include unsaturated esters, ketones, imides,nitriles,and sulfones. Cycloaddition occurs with complete cis stereospecificity (eq 1) which is consistent with a concerted mechanism. Dipolarophiles containing an endocyclic double bond afford fused bicyclic pyrrolidines, whereas substrates with an exocyclic double bond provide access to spirocyclic systems.

UsesN-Methoxymethyl-N-(trimethylsilylmethyl)benzylamine forms azomethine ylides which readily undergo [3+2] cycloaddition to α,-unsaturated esters affording N-benzyl substituted pyrrolidines in good yields. It reacts with asymmetric 1,3-dipolar cycloadditions in the practical, large-scale synthesis of chiral pyrrolidines. It is used in the the synthesis of 3-carboxy-1-azabicyclo[2.2.1]heptane derivatives, an important class of physiologically active compounds.

PreparationN-Methoxymethyl-N-(trimethylsilylmethyl)benzylamine is most conveniently prepared by treatment of benzylamine with chloromethyltrimethylsilane followed by formaldehyde and methanol. Access to higher ether homologs is achieved by replacing methanol with the appropriate alcohol. An alternate procedure involves alkylation of lithium N-benzyltrimethylsilymethylamide with methoxymethyl chloride.

Preparationmost conveniently prepared by treatment of benzylamine with chloromethyltrimethylsilane followed by formaldehyde and methanol.Access to higher ether homologs is achieved by replacing methanol with the appropriate alcohol. An alternate procedure involves alkylation of lithium N-benzyltrimethylsilymethylamide with methoxymethyl chloride.