Gold-catalyzed regioselective oxidation of terminal allenes: formation of α-methanesulfonyloxy methyl ketones

Abstract

SummarySynthetically useful α-methanesulfonyloxy methyl ketones are readily prepared in one-step from terminal allenes in fair to good yields. The chemistry relies on a gold-catalyzed intermolecular oxidation of the 1,2-diene unit using 3,5-dichloropyridine N-oxide as the oxidant. The reaction tolerates a range of functional groups and shows excellent regioselectivity.

Homogeneous Gold-Catalyzed Oxidation Reactions

“…In 2011, L. Zhang extended this type of oxidative gold catalysis to terminal allene substrates . As shown in Scheme , the reaction results in the formation of α-methanesulfonyloxy methyl ketone 31 .…”

“…57 In 2011, L. Zhang extended this type of oxidative gold catalysis to terminal allene substrates. 58 As shown in Scheme 16, the reaction results in the formation of α-methanesulfonyloxy methyl ketone 31. This product differs from those in Scheme 14B by having the α-MsO group attached at the non-methyl side aminooxazoles 32 (Scheme 17B).…”

Recent Developments in the Chemistry of Heteroaromatic N-Oxides

“…An early study is shown in Scheme 20. 48 Terminal allenes were converted into α-methanesulfonyloxy methyl ketones by using a highly active gold(I) cata-lyst, namely (4-CF 3 Ph) 3 PAuNTf 2 , and 3,5-dichloropyridine N-oxide as the oxidant. The proposed mechanism involves an initial gold-catalyzed regioselective addition of the Noxide to the allene sp-hybridized carbon, a subsequent protodeauration and a final S N 2′-type attack by mesylate.…”

Mechanistic insights and functionalization of alkynes in homogeneous gold catalysis.

“…4,7,28,[51][52][53][54][55][56][57][58] In particular, the gold-catalyzed oxygen transfer of a nucleophilic oxygen atom to an alkyne group is synthetically useful. [59][60][61][62][63][64][65] To further explore the reactivity of Au catalysts towards oxygen-atom transfer reactions, we investigated the gold-catalyzed addition of O-nucleophiles to alkynes to produce synthetically important vinyl ether products in excellent yields and regioselectivities at room temperature. Although these vinyl ethers are generally not stable enough to be isolated with standard silica gel chromatography, they were stable in our hands.…”

“…[59][60][61][62][63][64][65][178][179][180] In 2009, Asensio and co-workers applied the oxygen transfer concept in their intermolecular gold-catalyzed sulfoxide addition to alkynes that allowed the preparation of sulfur containing arenes (Scheme 16b).…”