Non-nanogold catalyzed aerobic oxidation of secondary amines to imines

Abstract

Bulk gold powder (approximately 10(3) nm particle size) is a highly active catalyst for the oxidative dehydrogenation of secondary amines to imines under the mild conditions of 1 atm O2 and 60-100 degrees C.

Conversions of Cyclic Amines to Nylon Precursor Lactams Using Bulk Gold and Fumed Silica Catalysts

“…12 In addition, we have demonstrated that bulk Au and 5% Au/Al 2 O 3 catalyze the oxidative dehydrogenation of cyclic amines with O 2 to form amidines (eq 1). 13,14 To the best of our knowledge, only two other examples have been reported in which cyclic amines are catalytically converted to amidines, and these both involved pyrrolidine. One used Pd black to catalyze the dehydrogenation of pyrrolidine under an Ar atmosphere at 80°C to give amidine-5 in 65% yield.…”

“…The amidines (amidine-5 and amidine-6) that are generated from the oxidative dehydrogenation of pyrrolidine and piperidine were prepared using larger scale reaction conditions. 13 The Authentic amidine-7 was prepared through an independent synthesis using a modified procedure involving the addition of hexamethyleneimine (211 mg, 2.11 mmol) to neat caprolactim methyl ether (250 mg, 1.97 mmol) (eq 4).…”

Facile and efficient one-pot synthesis of 2-arylbenzoxazoles using hydrogen tetrachloroaurate as catalyst under oxygen atmosphere

“…Note that the reaction could still proceed smoothly to give 3a in moderate yield even under air (entry 7). In the reaction, gold catalyst may act as a bifunctional catalyst; namely, it serves as an acid catalyst to help the cyclization process via activation of the imine group as well as an oxidative catalyst for the dehydrogenation of the in situ generated dihydrobenzoxazole with dioxygen (Zhu and Angelici, 2007).…”

Sodium tetrachloroaurate(III) dihydrate-catalyzed efficient synthesis of 1,5-benzodiazepine and quinoxaline derivatives

“…A variety of aromatic ring-tethered α-bromo ketones were investigated to establish the scope and generality of the reaction, and in all cases quinoxalines 5 were produced in good to excellent yields in the presence of NaAuCl 4 ·2H 2 O under mild reaction conditions. In the reaction, gold catalyst may act as a bifunctional catalyst; namely, it serves as a Lewis acid catalyst to help the cyclization process via activation of the carbonyl group (Yang et al, 2007) as well as an oxidative catalyst for the dehydrogenation of the in situ generated dihydroquinoxalines with dioxygen (Zhu and Angelici, 2007;Liu et al, 2009a).…”