Rasta Resin-PPh₃BnCl and its Use in Chromatography-Free Carbonyl Cyanosilylation Reactions

Abstract

Rasta resin-PPh₃BnCl, a new heterogeneous polystyrene-based phosphonium salt, has been synthesized and used to catalyze cyanosilylation reactions of aldehydes and ketones. It was found to be more efficient as a catalyst than a similar heterogeneous phosphonium salt anchored onto a polystyrene-based on the Merrifield resin architecture of 2% divinylbenzene cross-linking. In these reactions rasta resin-PPh₃BnCl was separated from the desired reaction product simply by filtration, and it could be reused without significant loss of catalytic activity numerous times.

polymer-supported catalyst - polystyrene - phosphonium salt - organocatalysis - cyanosilylation

References and Notes

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<A NAME="RW17310ST-12">12</A>

See Supporting Information for details.

<A NAME="RW17310ST-13">13</A>

General Procedure for Cyanosilylation Reactions To a solution of the aldehyde or ketone substrate (0.5 mmol) and TMSCN (0.75 mmol) in CHCl₃ was added 2 or 3 (0.025 mmol). The reaction mixture was stirred at 50 ˚C until TLC analysis indicated that the starting material was completely consumed. The reaction mixture was then filtered and the polymer-supported catalyst was washed with CH₂Cl₂ (2 × 50 mL). The combined filtrate was concentrated in vacuo to afford the desired product. All products were characterized by MS, ^¹H NMR, and ^¹³C NMR spectroscopy.