Reductions are fundamental and most frequently used chemical transformations in organic chemistry. Preparation of alcohols from reduction of aldehydes and ketones is a well-known reaction. Among the several methods for this transformation, hydride reductions are prominent in terms of yields and selectivities. Under hydride reductions, hydroboration is also an important method for the preparation of functionalized alcohols. In this regard various metal systems were reported to make this reaction more efficient with sustainable conditions.
Recently, numerous catalytic systems including transition, main group, and lanthanide complexes have been reported for the hydroboration of carbonyl and unsaturated hydrocarbons.1 However, some of these metal complexes are toxic, sensitive, expensive and requires tedious preparation of ligands. In order to overcome these issues, research is focusing on alternative catalytic systems using commercially available simple reagents for the economic and environmental concern.2
As a result, we have identified and reported selective hydroboration of aldehydes and ketones with readily available sodium hydride as catalysts.3 In continuation, here we would like to present our recent experimental results for the efficient hydroboration of aldehydes and ketones with pinacolborane using LiBr as catalyst (Scheme).
1. Chong, C. C.; Kinjo, R. ACS Catal. 2015, 5, 3238− 3259.
2. Wu, Y.; Shan, C.; Ying, J.; Su, J.; Zhu, J.; Liu, L. L.; Zhao, Y. Green Chem., 2017, 19, 4169-4175.
3. Shin, W. K.; Kim, H.; An, D. K. Tetrahedron. 2018, 74, 6310-6315