|Title||Organoboron protecting groups, and processes using same|
|Year of Publication||2022|
|Authors||Neto, NSaker, Wong, WWH, Simon, PMiguel, Castillo, JOmar|
|Assignee||University of Melbourne|
Organoboron reagents have become a staple of organic chemistry, largely due to the widespread use of Suzuki-Miyaura (SM) cross-coupling, a ubiquitous transition metal-catalysed C-C bond-forming reaction with wide scope and functional group tolerance. Since its discovery in 1979, the reaction has been studied and improved upon by a vast number of researchers.
A noteworthy development in the area is the disclosure of boronic acid protecting groups, which would ideally be inert to SM coupling as well as other reaction conditions, but are able to be unmasked to reveal an active boron species capable of SM coupling.
Examples of boronic acid protecting groups include N-methyliminodiacetic acid (MIDA) boronates and 1,8-diaminonaphthalene (DAN) boronamides.
MIDA boronates have found much success in iterative coupling for the synthesis of complex natural products, and have been central in a push for generalised synthetic methods inspired by solid phase peptide synthesis. However, MIDA boronates are not stable under basic aqueous conditions, which are often used to carry out SM coupling reactions.
DAN boronamides suffer from the disadvantage that they are somewhat sensitive to air and/or light, and typically require chromatography to purify the resulting protected boronamide.
It would be desirable to provide an improved or alternative boron protecting group. For example, it would be desirable provide alternative protecting groups for organoboron compounds such as boronic acids, which can be conveniently introduced, which have good stability to a range of reaction conditions including basic aqueous conditions, and which can be removed selectively.