Ammonia borane, Borane ammonia complex

This white solid can be used as an air-stable alternative to diborane. See also: trimethylamine borane

Recent Literature

A catalytic amount of titanium tetrachloride immensely accelerates the hydroboration-hydrolysis (reduction) of ketones with ammonia borane in diethyl ether at room temperature. The product alcohols are produced in very good yields within 30 min, even with ketones which typically requires 24 h or longer under uncatalyzed conditions.
P. V. Ramachandran, A. A. Alawaed, H. J. Hamann, J. Org. Chem., 2022, 87, 13259-13269.

Ammonia-borane reduces acids to alcohols at room temperature in the presence of catalytic TiCl₄. This process tolerates a variety of potentially reactive functional groups, including N-protected amino acids, nitriles and, to some extent, esters. Aliphatic acids can be selectively reduced in the presence of aromatic acids.
P. V. Ramachandran, A. A. Alawaed, H. J. Hamann, Org. Lett., 2022, 24, 8481-8486.

TiCl₄ mediates a facile and selective room temperature deoxygenation of both aromatic and aliphatic carboxylic esters to ethers in the presernce of BH₃-NH₃. This process is compatible with various potentially sensitive functional groups. Substituting TiCl₄ by BF₃-Et₂O alters the reaction pathway, reducing esters to alcohols.
P. V. Ramachandran, A. A. Alawaed, H. J. Hamann, Org. Lett., 2023, 25, 6902-6906.

Appropriate metal halide Lewis acids act as a carbonyl activator and halogen carrier for a deoxyhalogenation of aryl aldehydes, ketones, carboxylic acids, and esters in the presence of borane-ammonia as the reductant. Selectivity is accomplished by matching the stability of the carbocation intermediate with the effective acidity of the Lewis acid depending on the used solvent.
P. V. Ramachandran, A. A. Alawaed, H. J. Hamann, Org. Lett., 2023, 25, 4650-4655.

Trimethyl borate promotes a solvent-free reductive amination of aldehydes and ketones with aliphatic and aromatic amines in very good yields in the presence of ammonia borane as reductant.
P. V. Ramachandran, S. Choudhary, A. Singh, J. Org. Chem., 2021, 86, 4274-4280.

A wide range of nitriles were reduced to primary amines by 1.2 equiv of ammonia borane under thermal decomposition conditions without any catalyst to primary amines in very good yields. The reactions are environmentally benign with H₂ and NH₃ generated as byproducts. The reactions are also tolerant of many functional groups.
M. Ding, J. Chang, J.-X. Mao, J. Zhang, X. Chen, J. Org. Chem., 2022, 87, 16230-16235.

A cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes provides either Z- or E-alkenes based on a rational catalyst design. Substrates bearing a wide range of functional groups can be hydrogenated in good yields using catalyst loadings as low as 0.2 mol %.
S. Fu, N.-Y. Chen, X. Liu, Z. Shao, S.-P. Luo, Q. Liu, J. Am. Chem. Soc., 2016, 138, 8588-8594.

Nickel catalyzes a semihydrogenation of azoarenes with NH₃BH₃ to provide hydrazoarenes with good functional group tolerance and a high turnover frequency at room temperature. Results of control and deuterium-labeling experiments indicate that the ethanol hydroxyl and BH₃ groups each donated one hydrogen to this transfer hydrogenation, and the main byproducts were B(OEt)₃ and H₂.
D. Gong, D. Kong, Y. Li, C. Gao, L. Zhao, Org. Lett., 2023, 25, 4168-4172.

A transfer hydrogenation protocol for the reduction of quinolines, quinoxalines, pyridines, pyrazines, indoles, benzofurans, and furan derivatives with borane-ammonia (H₃N-BH₃) as the hydrogen source and a commercially available RuCl₃·xH₂O precatalyst provides the corresponding alicyclic heterocycles in very good isolated yields.
T. Bhatt, K. Natte, Org. Lett., 2024, 26, 866-871.

A borane catalyzed metal-free transfer hydrogenation of pyridines furnishes various piperidines in good yields with good cis-selectivities in the presence of ammonia borane as a hydrogen source. The ease in handling without requiring high pressure H₂ makes this transfer hydrogenation practical and useful.
Q. Zhou, L. Zhang, W. Meng, X. Feng, J. Yang, H. Du, Org. Lett., 2016, 18, 5189-5191.