Cobalt(II) Phthalocyanine-Catalyzed Highly Chemoselective Reductive Amination of Carbonyl Compounds in a Green Solvent
作者:Vishal Kumar、Upendra Sharma、Praveen K. Verma、Neeraj Kumar、Bikram Singh
DOI:10.1002/adsc.201100645
日期:2012.3.16
Cobalt phthalocyanine has been employed for the highlychemoselectivereductiveamination of aldehydes and ketones in ethanol as a greensolvent. A large range of functional groups such as nitro, acid, amide, ester, nitrile, halogen, lactone, methoxy, hydroxy, alkene, N‐benzyl, O‐benzyl and heterocyclic rings were well tolerated under the present reaction conditions.
A new nickel catalyzed cross‐electrophile coupling for accessing γ‐lactams (isoindolinones) as well as γ‐lactones (isobenzofuranones) via carbonylation with CO2 is documented. The protocol exploits the synergistic role of redox‐active Ni(II) complexes and AlCl3 as a CO2 activator/oxygen scavenger, leading to the formation of a wide range of cyclic amides and esters (28 examples) in good to high yields (up to 87%). A dedicated computational investigation revealed the multiple roles played by AlCl3. In particular, the simultaneous transient protection of the pendant amino group of the starting reagents and the formation of the electrophilically activated CO2‐AlCl3 adduct are shown to concur in paving the way for an energetically favorable mechanistic pathway.