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New potential of the reductive alkylation of amines

“…40, 41, 64 ± 67 The optimal reactant molar ratio carbonyl compound : amine : sodium borohydride is 1 : 1.1 : 1.1; acetic acid is used as both a reactant and the solvent for the preparation of a solution of the initial carbonyl compound. 64 The simultaneous introduction of sodium borohydride, aldehyde and amine into the reaction increases the yield of benzyl alcohol, which reaches 90% in the reaction of morpholine and 4-methoxycarbonylbenzaldehyde; therefore, NaBH 4 is added after the intermediate imine is stabilized in the form of iminium salt 16 (Scheme 12). 40…”

“…of acetic acid to form sodium triacetoxyhydroborate, and its participation in reductive amination has been experimentally demonstrated for the reaction of cyclohexanone and aniline as an example. 64 Since the reduction of imine to the target amine with sodium borohydride in acetic acid was only 20% complete after 10 h, and the reductive amination of cyclohexanone with aniline and sodium borohydride under the same conditions was completed in 1.5 h, it has been suggested 64 that the reaction mechanism in acetic acid is somewhat different from the conventional scheme, and it is likely that imine is not the only intermediate. At the same time, for the reaction of substituted benzaldehydes with aniline derivatives, 80% ± 85% of the intermediate imines are reduced at room temperature to benzylamines in 10 ± 20 h. 41 Since the NaBH 4 7AcOH system is able to reduce, in addition to the exocyclic C = N bond, multiple bonds in heterocyclic molecules, as well as carbonyl, nitro and nitrile groups, 68 conditions for selective synthesis of target amines should be carefully selected.…”

“…S-Benzylisothiuronium chloride (92) as an organic catalyst for enantioselective synthesis has been recently suggested for direct reductive alkylation with the use of Hantzsch ester (64); the reaction has been carried out for a wide range of ketones and arylamines (Scheme 56). 156 Scheme 56 * * * Significant progress has been achieved in the past decade in synthesis of amines by reductive alkylation.…”

“…(formed in the cascade of reactions beginning with the protonation of imine with a catalyst Ð chiral Brùnsted acid 71) with Hantzsch ester(64). Asymmetric induction is…”

Beta-ionone synthesis using anhydrous hydrogen fluoride

“…Thus, our investigation led to a new reagent that can be used for the synthesis of ct-ionone proceeding from pseudoionone and 13-ionone [6].…”