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19.5.10.1.1.2 Variation 2: Strecker Reactions under Nonaqueous Conditions

DOI: 10.1055/sos-SD-019-00171

North, M.Science of Synthesis, (200419287.

The procedures in Section 19.5.10.1.1.1 all involve the use of an aqueous solvent which is not always possible if the reactants contain hydrolyzable functional groups. Nonaqueous reaction conditions have been developed in which glacial acetic acid and methanol are used as the solvents.[‌23‌,‌24‌] This procedure works with both aldehydes and ketones, e.g. formation of (benzylamino)acetonitriles 4 (Scheme 3),[‌23‌] and is equally effective if the imine has been preformed.[‌25‌‌27‌] In particular, Barton and co-workers have used this cyanation procedure to prepare α-aminonitriles from imines which were themselves prepared in situ by the oxidation of a secondary amine with phenylselenic anhydride.[‌28‌] Tertiary amines can be electrochemically oxidized to iminium ions in methanol in the presence of sodium cyanide, thus providing a synthesis of α-aminonitriles from tertiary amines.[‌29‌] Other nonaqueous variations are the use of acetone cyanohydrin in acetone as the cyanide source for the formation of α-aminonitriles from preformed imines,[‌16‌] and diethyl phosphorocyanidate in conjunction with an aldehyde and a primary amine in tetrahydrofuran.[‌30‌,‌31‌] Treatment of an aldehyde or ketone with bis(dialkylamino)cyanoboranes [(R2N)2BCN] results in clean formation of N,N-dialkyl-substituted α-aminonitriles. Most combinations of alkylamines and carbonyl compounds react at room temperature, but reactions involving some ketones or large alkylamines require heating to 50°C.[‌32‌]

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