Palladium‐Catalyzed Selective Reduction of Carbonyl Compounds
Nabin Sarkar, Mamata Mahato, Sharanappa Nembenna
Abstract
Two new examples of structurally characterized β‐diketiminate analogues i.e., conjugated bis‐guanidinate (CBG) supported palladium(II) complexes, [LPdX] 2 ; [L= {(ArHN)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6‐Et 2 ‐C 6 H 3 ], X = Cl ( 1 ), Br ( 2 ) have been reported. The synthesis of complexes 1 – 2 was achieved by two methods. Method A involves deprotonation of LH by n BuLi followed by the treatment of LLi (insitu formed) with PdCl 2 in THF, which afforded compound 1 in good yield (75 %). In Method B, the reaction between free LH and PdX 2 (X = Cl or Br) in THF allowed the formation of complexes 1 (Yield 73 %) and 2 (Yield 52 %), respectively. Moreover, these complexes were characterized thoroughly by several spectroscopic techniques ( 1 H, 13 C NMR, UV/Vis, FT‐IR, and HRMS), including single‐crystal X‐ray structural and elemental analyses. In addition, we tested the catalytic activity of these complexes 1 – 2 for the hydroboration of carbonyl compounds with pinacolborane (HBpin). We observed that compound 1 exhibits superior catalytic activity when compared to 2 . Compound 1 efficiently catalyzes various aldehydes and ketones under solvent‐free conditions. Furthermore, both inter‐ and intramolecular chemoselectivity hydroboration of aldehydes over other functionalities have been established.