Gold‐Catalyzed Oxidative Ring Expansions and Ring Cleavages of Alkynylcyclopropanes by Intermolecular Reactions Oxidized by Diphenylsulfoxide

Li, Chia‐Wen; Pati, Kamalkishore; Lin, Guorong; Sohel, Shariar Md. Abu; Hung, Hsiao-Hua; Liu, Rai‐Shung

doi:10.1002/anie.201004647

Cited by 219 publications

(61 citation statements)

References 49 publications

(15 reference statements)

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“…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 .…”

Section: Resultsmentioning

confidence: 99%

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

Ji¹,

Nelson²,

Zhang³

2013

Beilstein J. Org. Chem.

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SummaryGold-catalyzed intermolecular oxidation of carboxylates of primary or secondary propargylic alcohols are realized with excellent regioselectivity, which is ascribed to inductive polarization of the C–C triple bond by the electron-withdrawing carboxy group. The gold carbene intermediates thus generated undergo selective 1,2-acyloxy migration over a 1,2-C–H insertion, and the selectivities could be dramatically improved by the use of a P,S-bidentate ligand, which is proposed to enable the formation of tris-coordinated and hence less electrophilic gold carbene species. α-Carboxy α,β-unsaturated ketones/aldehydes can be obtained with fair to excellent yields.

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Section: Resultsmentioning

confidence: 99%

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

Ji¹,

Nelson²,

Zhang³

2013

Beilstein J. Org. Chem.

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“…Liu 29 reported highly regioselective Au(I)-catalyzed oxidative ring-expansions of cyclopropyl-substituted ynamides 123 using Ph 2 SO (Scheme 23). The ring expansion is not believed to proceed through an α -keto gold carbenoid intermediate but through 124 .…”

Section: Transition Metal Mediated Cyclizationsmentioning

confidence: 99%

Ynamides in Ring Forming Transformations

et al. 2013

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Conspectus The ynamide functional group activates carbon-carbon triple bonds through an attached nitrogen atom that bears an electron-withdrawing group. As a result, the alkyne has both electrophilic and nucleophilic properties. Through the selection of the electron-withdrawing group attached to nitrogen chemists can modulate the electronic properties and reactivity of ynamides, making these groups versatile synthetic building blocks. The reactions of ynamides also lead directly to nitrogen-containing products, which provides access to important structural motifs found in natural products and molecules of medicinal interest. Therefore, researchers have invested increasing time and research in the chemistry of ynamides in recent years. This Account surveys and assesses new organic transformations involving ynamides developed in our laboratory and in others around the world. We showcase the synthetic power of ynamides for rapid assembly of complex molecular structures. Among the recent reports of ynamide transformations, ring-forming reactions provide a powerful tool for generating molecular complexity quickly. In addition to their synthetic utility, such reactions are mechanistically interesting. Therefore, we focus primarily on the cyclization chemistry of ynamides. This Account highlights ynamide reactions that are useful in the rapid synthesis of cyclic and polycyclic structural manifolds. We discuss the mechanisms active in the ring formations and describe representative examples that demonstrate the scope of these reactions and provide mechanistic insights. In this discussion we feature examples of ynamide reactions involving radical cyclizations, ring-closing metathesis, transition metal and non-transition metal mediated cyclizations, cycloaddition reactions, and rearrangements. The transformations presented rapidly introduce structural complexity and include nitrogen within, or in close proximity to, a newly formed ring (or rings). Thus, ynamides have emerged as powerful synthons for nitrogen-containing heterocycles and nitrogen-substituted rings, and we hope this Account will promote continued interest in the chemistry of ynamides.

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“…In path a, cyclometalation of 1 a is followed by alkyne coordination and RhÀC migratory insertion to afford the seven-member rhodacyclic intermediate A. Although the observed regioselectivity of the coupling of 1-phenyl-1propyne agrees with this mechanism (electronic effect) and with that in gold-catalyzed OAT reactions, [19] the observed regioselectivity for 3 oj and 3 oj' in this eletronically biased push-pull alkyne argues against this mechanism. Tautomerization or slippage produces the isolable h 3 -benzyl intermdiate 8.…”

Section: Angewandte Zuschriftenmentioning

confidence: 81%

ChemInform Abstract: Rhodium(III)‐Catalyzed C—C and C—O Coupling of Quinoline N‐Oxides with Alkynes: Combination of C—H Activation with O‐Atom Transfer.

Zhang

2015

ChemInform

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[Cp*Rh III ]-catalyzed C À H activation of arenes assisted by an oxidizing NÀO or NÀN directing group has allowed the construction of a number of hetercycles. In contrast, a polar NÀO bond is well-known to undergo O-atom transfer (OAT) to alkynes. Despite the liability of N À O bonds in both C À H activation and OAT, these two important areas evolved separately. In this report, [Cp*Rh III ] catalysts integrate both areas in an efficient redox-neutral coupling of quinoline N-oxides with alkynes to afford a-(8-quinolyl)acetophenones. In this process the NÀO bond acts as both a directing group for CÀH activation and as an O-atom donor.

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Gold‐Catalyzed Oxidative Ring Expansions and Ring Cleavages of Alkynylcyclopropanes by Intermolecular Reactions Oxidized by Diphenylsulfoxide

Cited by 219 publications

References 49 publications

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

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

Ynamides in Ring Forming Transformations

ChemInform Abstract: Rhodium(III)‐Catalyzed C—C and C—O Coupling of Quinoline N‐Oxides with Alkynes: Combination of C—H Activation with O‐Atom Transfer.

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