Iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl , efficiently catalyzed the insertion of carbenes derived from methyl 2-phenyldiazoacetates into O-H bonds of aliphatic and aromatic alcohols, with yields generally above 80%. Although the analogous N-H insertions are rapid at room temperature, the O-H insertion reactions are slower and required heating in refluxing methylene chloride for about 8 hours using 1.0 mol.% catalyst. Fe(TPP)Cl was also found to be effective for tandem N-H insertion/cyclization reactions when 1,2-diamines and 1,2-alcoholamines were treated with diazo reagents to give piperazinones and morpholinones and related analogs such as quinoxalinones and benzoxazin-2-ones. This approach provides a new one-pot route for synthesizing these classes of heterocyclic compounds.
Bulk gold powder (∼50 μm) and alumina-supported gold catalyzed the oxidative dehydrogenation of 5-, 6-, and 7-membered cyclic amines to amidines. These amidines were hydrolyzed upon treatment with Aerosil 200 (fumed silica gel) and water, producing lactams in 42-73% yields and amines in 36-63% yields. The gold and Aerosil 200 catalysts could also be combined in a one-pot reaction to catalyze the conversion of cyclic amines to lactams in yields up to 51%.
Bulk gold powder (∼5-50 μm particles) catalyzes the reactions of isocyanides with amines and amine Noxides to produce ureas. The reaction of n-butyl isocyanide (nBu-N≡C) with di-n-propylamine and Nmethylmorpholine N-oxide in acetonitrile, which was studied in the greatest detail, produced 3-butyl-1,1-dipropylurea (O═C(NHnBu)(NnPr2)) in 99% yield at 60 °C within 2 h. Sterically and electronically different isocyanides, amines, and amine N-oxides react successfully under these conditions. Detailed studies support a two-step mechanism that involves a gold-catalyzed reaction of adsorbed isocyanide with the amine N-oxide to form an isocyanate (RN═C═O), which rapidly reacts with the amine to give the urea product. These investigations show that bulk gold, despite its reputation for poor catalytic activity, is capable of catalyzing these reactions.
Disciplines
Chemistry
CommentsReprinted (adapted) with permission from Organometallics 31 (2012) ABSTRACT: Bulk gold powder (∼5−50 μm particles) catalyzes the reactions of isocyanides with amines and amine N-oxides to produce ureas. The reaction of n-butyl isocyanide ( n Bu−NC) with di-n-propylamine and N-methylmorpholine N-oxide in acetonitrile, which was studied in the greatest detail, produced 3-butyl-1,1-dipropylurea (OC(NH n Bu)(N n Pr 2 )) in 99% yield at 60°C within 2 h. Sterically and electronically different isocyanides, amines, and amine N-oxides react successfully under these conditions. Detailed studies support a two-step mechanism that involves a gold-catalyzed reaction of adsorbed isocyanide with the amine N-oxide to form an isocyanate (RNCO), which rapidly reacts with the amine to give the urea product. These investigations show that bulk gold, despite its reputation for poor catalytic activity, is capable of catalyzing these reactions.
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