This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Many molecules in living organisms and pharmaceuticals share a structure called a β-amino alcohol, in which an amino group and a hydroxyl group sit on neighboring carbon atoms. These groups, important building blocks in biology and medicine, are found in compounds such as sphingosine and ephedrine.
In such molecules, the exact three-dimensional arrangement of atoms can greatly affect their biological activity, even if they have the same chemical formula. Thus, chemists seeking to synthesize them require techniques that produce the specific version they need. One common method is the well-studied Henry reaction, which joins an aldehyde and a nitroalkane to form a β-nitro alcohol that can later be reduced to a β-amino alcohol.
However, most catalyst-based approaches to the Henry reaction produce what's known as the syn form, where the two groups point to the same side of the molecule. The anti form, in which groups point to opposite sides of the molecule, has proven much harder to synthesize reliably. To address this challenge, a research team led by professor Takayoshi Arai from the Graduate School of Science at Chiba University, Japan, has designed a new catalyst that favors the anti form by leveraging several types of molecular interactions in a single system.
Their study, which was published online in Angewandte Chemie International Edition, was co-authored by Dr. Hidesato Iwama, both from the Graduate School of Science at Chiba University. The researchers built their catalyst, called o-X-F4-PyBidine-Ni(OTf)2 (X = Br or I), around a nickel complex containing a molecular structure called PyBidine.
They introduced either bromine or iodine at a specific position on the catalyst to create a site capable of halogen bonding. In halogen bonding, a positive charge called the σ-hole forms on the surface of a halogen atom and establishes electrostatic interactions with the functional groups. This noncovalent interaction helped position the aldehyde in a specific orientation.
Hydrogen bonding, a more familiar attractive force that arises between a hydrogen atom and an electronegative atom, also helped hold the aldehyde in place and activate it. Meanwhile, nickel, alongside a base called triethylamine, activated the nitroalkane. Together, these interactions positioned the two reacting molecules in a favorable stretched-out arrangement that led to the anti-product.
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