Generation and Cycloaddition of Polymer-Supported Azomethine Ylide via a 1,2-Silatropic Shift of α-Silylimines:  Traceless Synthesis of Pyrrolidine Derivatives

Abstract

The 1,3-dipolar cycloaddition of polymer-supported azomethine ylides to dipolarophiles gave pyrrolidine derivatives in good yields. The azomethine ylides were generated from resin-bound alpha-silylimines via a 1,2-silatropic shift. The features of this method are not only a traceless synthesis but also a unique solid-phase route to pyrrolidines with extensive diversity. [reaction: see text]

Solid Phase and Combinatorial Chemistry in the Heterocyclic Field

“…Thermal 1,2-silatropic shift affords 122, which reacts in situ with the corresponding dipolarophiles to provide pyrrolidines 123. A further element of diversity can be introduced into the pyrrolidine ring during the cleavage step (multidirectional electrophilic cleavage) with different electrophiles (HCl, acid chlorides, allyl iodide, and so on) to furnish collections of pyrrolidines of type 124 in good yields (Scheme 28.38) [159]. Substituted pyrroles are commonly found in natural products [160,161], drugs [162,163], conducting materials [164,165] and insecticides [166].…”

Diversity Linker Units for Solid‐Phase Organic Synthesis

“…[64] Following silatropic ylide generation, a [3+2] cycloaddition reaction afforded a series of pyrrolidine derivatives 99 (Scheme 31). Cleavage was achieved with a range of electrophiles.…”

CC Bond‐Forming Reactions

“…The discovery of a new method for generating azomethine ylides from a-silylimines, via a 1,2-sigmatropic shift of the silyl group onto the nitrogen of the imino group, prompted the application of this strategy on a solid phase [294]. The precursor (255) is prepared by treating freshly prepared solid-supported silyl chloride with an azaallyl anion.…”

“…Cycloaddition with azomethines generated in situ on a solid phase (Scheme 56) [294]: To a suspension of polymer-supported a-silylimine (255) (0.643 mmol) in toluene (4.5 mL) was added N-phenylmaleimide (445 mg, 2.57 mmol). The mixture was heated to 180°C in a sealed tube for 6 h. After cooling to r. t., the resin was washed as follows: 1.…”