OBn

OBn is an abbreviation that commonly denotes an alkoxyborane, a class of organoboron compounds in which a boron atom is bound to an alkoxy group (OR) and two hydroxyl groups. The general structure can be written as R–O–B(OH)₂, where R is an organic substituent such as a methyl, phenyl, or more complex alkyl or aryl group. These reagents are prepared by the reaction of boric acid or B(OH)₃ with an alcohol in the presence of a base or by reduction of borates.

Alkoxyboranes serve as useful building blocks in organic synthesis. They can act as nucleophilic boron species in reactions such as the Miyaura borylation, the Suzuki–Miyaura cross‑coupling, and various carbon–carbon bond forming transformations. The hydroxyl groups on OBn are often activated toward transmetalation, while the alkoxy substituent can be tuned to influence the electronic properties and steric bulk of the boron center. In addition, OBn reagents are employed in the synthesis of boronic acids, diols, and in the preparation of boron‑based protecting groups for alcohol and phenol functionalities.

Typical examples include MeO–B(OH)₂ (methyl alkoxyborane), PhO–B(OH)₂ (phenyl alkoxyborane), and more specialized reagents such as O‑Bn–B(OH)₂, where the alkoxy group contains a benzyloxy moiety used in selective protection‑deprotection strategies. The chemistry of OBn compounds is extensively documented in the literature on organoboron chemistry, with key reviews appearing in journals such as the Journal of the American Chemical Society, Organic Letters, and the European Journal of Organic Chemistry.