Gold(I)-Catalyzed Intermolecular Oxyarylation of Alkynes: Unexpected Regiochemistry in the Alkylation of Arenes

Abstract

The reaction between acetylenes and sulfoxides, studied as a test case for gold-catalyzed intermolecular addition, provides the oxyarylation compounds 3 in good yields. Unpredictably, in all cases a single regioisomer arising from the electrophilic aromatic alkylation at the position adjacent to the sulfur atom is obtained instead of the expected Friedel-Crafts regioisomer. A new concerted mechanism based on DFT calculations is proposed to account for the products in this intermolecular gold(I)-catalyzed reaction.

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

“…The former process would eventually lead to the formation of the enones 6 [31]. Due to hydrolysis, only under thermal and anhydrous conditions products derived from the latter processes can be predominantly formed [32]; under our conditions (at ambient temperature and without exclusion of moisture), the enone 6 was indeed detected but in a minute amount, suggesting that the 1,2-acyloxy migration might be an even less meaningful event in the reaction; b) it is known that the gold carbenes of type B can be readily oxidized by Ph 2 S=O [33], which, however, is an inefficient oxidant for generating α-oxo gold carbenes of type A via alkyne oxidation [34–35]; when the N -oxide 3 is replaced by the sulfoxide, 5a-OAc was formed in only 5% yield even at 60 °C after 12 h (Scheme 4); moreover, the major product in the reaction was the expected enone 6 (56% yield, 88% conversion) due to a dominant gold-catalyzed 3,3-rearrangement; c) this alternative could not rationalize the formation of 5a-H .…”

Gold-Catalyzed Nitrene Transfer to Activated Alkynes: Formation of α,β-Unsaturated Amidines

“…Although there are still some ambiguities regarding discrete reaction mechanisms, 1 this strategy has been applied successfully in intramolecular transformations using tethered oxygen-delivering oxidants such as sulfoxides, 2 N -oxides, 1b,3 nitrones 4 and epoxide 5 where their oxygen-less parts (i.e., Y) behave as nucleofuges (Scheme 1A). Attempts to realized intermolecular versions of this strategy using external sulfoxides 6 led to 3,3-rearrangements instead and the intermediacy of α-oxo gold carbenes was ruled out both by experiments and via calculations. We discovered, however, that pyridine N -oxides and quinoline N -oxides were suitable external oxidants for the generation of these reactive gold intermediates intermolecularly, thus offering valuable opportunities to replace hazardous and potentially explosive diazo ketones with benign alkynes in gold carbene chemistry (Scheme 1B).…”

Gold- and Iodine-Mediated Internal Oxygen Transfer of Nitrone- and Sulfoxide-Functionalized Alkynes

“…13 C NMR (125 MHz, CDCl 3 ): δ 149. 8,149.2,134.7,133.4,130.9,130.1,123.9,123.5,72.9,61.5,54.5,43.0,30.3. IR (cm À1 ): 1686,1638,1467,1458,1271,1049,1009,760,675 8, 147.9, 134.8, 133.3, 130.9, 129.9, 123.8, 123.5, 77.9, 61.6, 54.4, 36.4, 32.1, 30.3 8, 147.9, 141.2, 135.0, 133.3, 130.9, 130.3, 130.1, 128.1, 127.8, 124.5, 123.5, 71.6, 54.4 1, 150.0, 134.6, 133.7, 131.0, 130.6, 123.9, 123.5, 54.7, 49.5, 30.4 Representative Synthesis of Compounds 7aÀc.…”