Polymer Supported Triphenylphosphine-Palladium Acetate Complex PS-TPP-Pd(OAc)2 as a Heterogeneous and Reusable Catalyst for Indirect Reductive Amination of Aldehydes

Abstract

Indirect reductive amination of aldehydes, catalyzed by polymer supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc) 2 catalyst have been developed. The imine is prepared with molecular sieves in the first stage, followed by reduction with potassium formate catalyzed by PS-TPP-Pd(OAc) 2 . The recovered catalyst could be reused for four consecutive cycles without loss in activity and provided an excellent yield of the desired products.

Polymer-supported triphenylphosphine: application in organic synthesis and organometallic reactions

“…Aldehydes and ketones have been shown to undergo indirect reductive amination using polymer-supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc) 2 (10 mol% loading) as a heterogeneous and recyclable catalyst and sodium formate as a reducing agent (Table 33). 96 The catalyst was easily prepared and isolated quantitatively as a yellowish solid by heating a mixture of PS-TPP and Pd(OAc) 2 (P/Pd ratio of 4 : 1) in DMF to 45-50 C for 4 h. The protocol involved two stages where the imine or iminium ion is rst formed from the aldehyde or ketone, respectively, followed by PS-TPP-Pd(OAc) 2 -mediated catalytic reduction with sodium formate. Aromatic aldehydes and ketones gave higher yields than the corresponding aliphatic substrates and the catalyst was reusable over four consecutive cycles without any profound loss of catalytic activity.…”

One‐Pot Reductive Amination of Aromatic Aldehydes in [Et3NH][HSO4] using Sodium Borohydride and A Mechanistic Investigation using Computational Method

“…Reductive amination [19–26] of carbonyl compounds has been identified as the most effective and versatile method to synthesize secondary amines, surpassing several other methods such as Gabriel synthesis, [27–28] reduction of nitrogen‐containing compounds, [29–32] and alkylation of ammonia and amines [33–34] . Several catalyst systems and reducing reagents have been explored in reductive amination, following direct [35–42] as well as indirect procedures [43–44] . However, most of them suffered from one or more drawbacks, such as harsh reaction conditions, use of expensive and flammable reagents, complex and toxic metal catalyst systems, poor yields in spite of high conversion of aldehydes in some cases, low chemical selectivity, generation of toxic byproducts, and so on [45–51] .…”

Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis

“…These Pd species may redeposit onto the polystyrene support and are recyclable even though a slight increase in the size of supported Pd particles occurs during the reaction. Ekbote et al [9] report a polymer supported triphenylphosphine-palladium acetate complex catalyst for the indirect reductive amination of aldehydes. The catalyst is highly selective to the formation of the desired products and can be recovered and recycled without loss in the activity.…”