Metal‐Catalyzed Cycloisomerization and Tandem Oxycyclization/Hydroxylation of Alkynols: Synthesis of Nonfused, Spiranic and Fused Oxabicyclic β‐Lactams

Alcaide, Benito; Almendros, Pedro; Campo, Teresa Martínez del; Carrascosa, Rocío

doi:10.1002/ejoc.201000710

Cited by 25 publications

(14 citation statements)

References 55 publications

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“…At this stage, the reaction proceeds via as econd cyclization process involving the alkynyl lateral group and the oxygen to form the dihydrofuran cycle [23] which actually we computed to be extremelyt hermodynamically favored (DE = À119.16 kcal mol À1 ,see the Supporting Information).…”

Section: Resultsmentioning

confidence: 88%

Silver(I) Oxide‐/DBU‐Promoted Synthesis of Dihydrofuran Units through Allenyl Silver Formation

Perfetto

Allievi

et al. 2020

Chemistry A European J

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Af ormal [3+ +2] cyclization mediated by silver(I) oxide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is described herein. Through ab road variety of carbonyl compounds, this system can promote cyclization reactions with high yield (up to 85 %) and diastereoselectivity(up to 95:5) for as traightforward access to complex and congestedd ihydrofuran derivatives in one step under mild conditions. Based on DFT studies, the proposed mechanism would involve an allenyl silver intermediate.

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Section: Resultsmentioning

confidence: 88%

Silver(I) Oxide‐/DBU‐Promoted Synthesis of Dihydrofuran Units through Allenyl Silver Formation

Perfetto

Allievi

et al. 2020

Chemistry A European J

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“…33 It was found that the use of gold catalysis selectively led to a tandem cycloisomerization/hydroxylation, affording structures 36 and 39, while the use of silver-based systems yielded . PtBr 4 was also tested as catalyst for this procedure, providing similar results as the ones for gold.…”

Section: Scheme 10mentioning

confidence: 99%

Gold catalyzed oxycyclizations of alkynols and alkyndiols

2011

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Alkynols and alkyndiols represent excellent building blocks for oxycyclization reactions, leading to a large number of different cyclic structures in one single step. Recently, the use of gold salts and gold complexes has been introduced as an alternative to the traditional methods, providing mild reaction conditions and high group compatibility. This overview focuses on the most recent achievements on gold-catalyzed oxycyclizations, both from alkynols and alkyndiols, and their use in different cascade processes and total synthesis.

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“…22 In this context, the preparacion 19 of fused oxabicyclic β-lactams using gold catalysis through a tandem oxycyclization/hydroxylation of 2-azetidinone-linked alkynols has been accomplished. 23 The reaction of 2-azetidinone-tethered bishomopropargylic alcohol 40 in the presence of catalytic amounts of AuCl 3 provided bicycle 41…”

Section: Gold-catalyzed Oxycyclizations Of Alkynol Derivativesmentioning

confidence: 99%

Gold-Catalyzed Cyclization Reactions of Allenol and Alkynol Derivatives

2014

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A lthough gold is chemically inert as a bulk metal, the landmark discovery that gold nanoparticles can be effective catalysts has opened up new and exciting research opportunities in the field. In recent years, there has been growth in the number of reactions catalyzed by gold complexes [gold(I) and gold(III)], usually as homogeneous catalysts, because they are soft Lewis acids. In addition, alkynes and allenes have interesting reactivities and selectivities, notably their ability to produce complex structures in very few steps. In this Account, we describe our work in gold catalysis with a focus on the formation of CÀC and CÀO bonds using allenes and alkynes as starting materials. Of these, oxa-and carbo-cyclizations are perhaps the best known and most frequently studied. We have divided those contributions into sections arranged according to the nature of the starting material (allene versus alkyne).Gold-catalyzed carbocyclizations in allenyl C2-linked indoles, allenyl-β-lactams, and allenyl sugars follow different mechanistic pathways. The cyclization of indole-tethered allenols results in the efficient synthesis of carbazole derivatives, for example. However, the compound produced from gold-catalyzed 9-endo carbocyclization of (aryloxy)allenyl-tethered 2-azetidinones is in noticeable contrast to the 5-exo hydroalkylation product that results from allenyl sugars.We have illustrated the unusual preference for the 4-exo-dig cyclization in allene chemistry, as well as the rare β-hydride elimination reaction, in gold catalysis from readily available R-allenols. We have also observed in γ-allenols that a (methoxymethyl)oxy protecting group not only masks a hydroxyl functionality but also exerts directing effects as a controlling unit in a gold-catalyzed regioselectivity reversal. Our recent work has also led to a combined experimental and computational study on regioselective gold-catalyzed synthetic routes to 1,3-oxazinan-2-ones (kinetically controlled products) and 1,3-oxazin-2-one derivatives (thermodynamically favored) from easily accessible allenic carbamates.In addition, we discuss the direct gold-catalyzed cycloketalization of alkynyldioxolanes, as well as aminoketalization of alkynyloxazolidines. We performed labeling studies and density functional calculations to gain insight into the mechanisms of the bis-heterocyclization reactions. We also describe the controlled gold-catalyzed reactions of primary and secondary propargylic hydroperoxides with a variety of nucleophiles including alcohols and phenols, allowing the direct synthesis of β-functionalized ketones. Through computations and 18 O-labeling experiments, we discovered various aspects of the controlled reactivity of propargylic hydroperoxides with external nucleophiles under gold catalysis. The mechanism resembles a MeyerÀSchuster rearrangement, but notably, the presence and geometry characteristics of the OOH functional group allow a new pathway to happen, which cannot apply to propargylic alcohols.

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Metal‐Catalyzed Cycloisomerization and Tandem Oxycyclization/Hydroxylation of Alkynols: Synthesis of Nonfused, Spiranic and Fused Oxabicyclic β‐Lactams

Cited by 25 publications

References 55 publications

Silver(I) Oxide‐/DBU‐Promoted Synthesis of Dihydrofuran Units through Allenyl Silver Formation

Silver(I) Oxide‐/DBU‐Promoted Synthesis of Dihydrofuran Units through Allenyl Silver Formation

Gold catalyzed oxycyclizations of alkynols and alkyndiols

Gold-Catalyzed Cyclization Reactions of Allenol and Alkynol Derivatives

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