α-Picoline-Borane, 2-Methylpyridine Borane, PICB
Pic-BH3 is a very stable solid that can be stored without noticable decomposition. This reagent is an excellent alternative for reductive aminations in methanol, water, or even under solvent-free conditions.
A mild and efficient one-pot reductive amination of aldehydes and ketones with amines using α-picoline-borane as a reducing agent in the presence of small amounts of AcOH is described. The reaction has been carried out in MeOH, in H2O, and in neat conditions. This is the first successful reductive amination in water and in neat conditions.
S. Sato, T. Sakamoto, E. Miyazawa, Y. Kikugawa, Tetrahedron, 2004, 60, 7899-7906.
Reductive aminations of shelf-stable bisulfite addition compounds of aldehydes can be run under aqueous micellar catalysis conditions with readily available α-picolineborane as the stoichiometric hydride source. Recycling of the aqueous reaction medium is easily accomplished.
X. Li, K. S. Iyer, R. R. Thakore, D. K. Leahy, J. D. Bailey, B. H. Lipshutz, Org. Lett., 2021, 23, 7205-7208.
Half-sandwich ruthenium complexes activate terminal alkynes toward anti-Markovnikov hydration and reductive hydration under mild conditions. Propargylic alcohols can be converted to 1,3-diols in high yield and with retention of stereochemistry at the propargylic position. The method is also amenable to formal anti-Markovnikov reductive amination and oxidative hydration reactions to access linear amines and carboxylic acids, respectively.
M. Zeng, S. B. Herzon, J. Org. Chem., 2015, 80, 8604-8618.
An efficient method for the direct reductive alkylation of hydrazine derivatives with α-picoline-borane provided various N-alkylhydrazine derivatives upon fine-tuning of the substrates and the reagent equivalency in a one-pot manner. The method was applied to the synthesis of active pharmaceutical ingredients of therapeutic drugs such as isocarboxazid.
Y. Kawase, T. Yamagishi, J.-y. Kato, T. Kutsuma, T. Kataoka, T. Iwakuma, T. Yokomatsu, Synthesis, 2014, 46, 455-464.