Palladium-Catalyzed Carbonylation of Amines with Mo(CO)₆ as the Carbonyl Source

Abstract

Catalytic carbonylation of transition metals is widely used as an effective means to synthesize carbonyl-containing compounds. In this article, we introduce a method for the synthesis of N,N′-diphenyl urea and N-phenyl carbamate by transition-metal-catalyzed carbonylation. Here, we use Mo(CO)6 as a safe and stable carbonyl source to introduce the reaction to produce carbonylation products and achieve the selective formation of N,N′-diphenylurea and N-phenylcarbamate under mild conditions. Mechanistic investigations suggested that the reaction proceeded through sequential amine C–H bond activation, carbonyl insertion, nucleophilic attack, and oxidation of Pd(0) with Cu(OAc)2 to generate N-phenyl carbamate and N,N-diphenyl urea products. Moreover, the indenones obtained with Mo(CO)6 as a CO surrogate can be functionalized to form synthetic useful derivatives via an environmentally friendly way.

Access to carbamates and o-aminobenzoates via oxidative carbonylation of amines with CO and alcohols under rhodium/copper catalysis

“…In addition, under standard conditions, the reaction of N -phenylformamide 8 14 with 2a only afforded a low yield of 3aa . These results indicated that the urea 4 a ,7 is the most likely intermediate in the carbonylative synthesis of carbamates.…”

“…1 Thus, the development of an efficient methodology for accessing structurally diverse carbamates has attracted considerable attention from both academic and industrial perspectives. Among the numerous protocols developed, 2–8 catalytic carbonylative coupling of amines and alcohols with CO for the synthesis of carbamates has been extensively studied in terms of their atom and step economy. 3–8 In this context, while notable advances have been achieved regarding the oxidative carbonylation of amines with alcohols and CO using different transition metal catalysts (Pd, Rh, Au, etc .…”

“…Among the numerous protocols developed, 2–8 catalytic carbonylative coupling of amines and alcohols with CO for the synthesis of carbamates has been extensively studied in terms of their atom and step economy. 3–8 In this context, while notable advances have been achieved regarding the oxidative carbonylation of amines with alcohols and CO using different transition metal catalysts (Pd, Rh, Au, etc . ), most well-established studies have focused on primary alcohols under high CO pressure (Scheme 1a).…”

“…Very recently, an interesting example of the carbonylation of aromatic primary amines with methanol or ethanol using Mo(CO) 6 as a CO surrogate was discovered in a Pd/Cu catalytic system. 7 Unfortunately, no carbamate product was observed when aliphatic amines or secondary alcohols were used as the substrate. Thus, the oxidative carbonylation of amines with sterically hindered tertiary alcohols is extremely challenging.…”

How To Get Isocyanate?

“…The oxidative carbonylation of amines necessitates the presence of oxidants, such as molecular oxygen, − nitro compounds, iodine, quinone, its derivatives, or unsaturated organic substances. , Among these, molecular oxygen serves as the primary oxidant. This reaction entails a mixture of CO and O 2 , which can be potentially explosive within a specific concentration range.…”