Molecules

Research

Jump to: Review

14 pages, 2176 KiB

Open AccessArticle

One-Step Green Synthesis of Isoeugenol Methyl Ether from Eugenol by Dimethyl Carbonate and Phase-Transfer Catalysts

by Zhihai Zhang, Yin Gong, Xinru Xue, Mengshuang Hu, Min Zhou, Yao Zhao and Zhiqiang Hu

Molecules 2024, 29(2), 551; https://doi.org/10.3390/molecules29020551 - 22 Jan 2024

Viewed by 1025

Abstract

In this paper, the green synthesis of isoeugenol methyl ether (IEME) from eugenol by O-methylation and isomerization is completed using a one-step green process. In the methylation reaction, dimethyl carbonate (DMC) was used as a green chemistry reagent instead of the traditional [...] Read more.

In this paper, the green synthesis of isoeugenol methyl ether (IEME) from eugenol by O-methylation and isomerization is completed using a one-step green process. In the methylation reaction, dimethyl carbonate (DMC) was used as a green chemistry reagent instead of the traditional harmful methylation reagents, in accordance with the current concept of green chemistry. The phase transfer catalyst (PTC) polyethylene glycol 800 (PEG-800) was introduced into the isomerization reaction to break the barrier of difficult contact between solid and liquid phases and drastically reduce the reaction conditions by shortening the reaction time and reducing the alkalinity of the reaction system. The catalytic systems for the one-step green synthesis of IEME were screened, and it was shown that the catalytic system “K₂CO₃ + PEG-800” was the most effective. The effects of reaction temperature, n(DMC):n(eugenol) ratio, n(PEG-800):n(eugenol) ratio, and n(K₂CO₃):n(eugenol) ratio on eugenol conversion, IEME yield, and IEME selectivity were investigated. The results showed that the best reaction was achieved at a reaction temperature of 140 °C, a reaction time of 3 h, a DMC drip rate of 0.09 mL/min, and n(eugenol):n(DMC):n(K₂CO₃):n(PEG-800) = 1:3:0.09:0.08. As a result of the conversion of 93.1% of eugenol to IEME, a yield of 86.1% IEME as well as 91.6% IEME selectivity were obtained. Full article

(This article belongs to the Special Issue Application of Cascade/Tandem Reactions in Green Organic Synthesis)

► Show Figures

Graphical abstract

11 pages, 1501 KiB

Open AccessArticle

One-Pot Synthesis of 3,4-Dihydrocoumarins via C-H Oxidation/Conjugate Addition/Cyclization Cascade Reaction

by Dae Young Kim

Molecules 2023, 28(19), 6853; https://doi.org/10.3390/molecules28196853 - 28 Sep 2023

Viewed by 715

Abstract

The 3,4-dihydrocoumarin derivatives were obtained from 2-alkyl phenols and oxazolones via C–H oxidation and cyclization cascade in the presence of silver oxide (Ag₂O) and p-toluenesulfonic acid as a Brønsted acid catalyst. This approach provides a one-pot strategy to synthesize the [...] Read more.

The 3,4-dihydrocoumarin derivatives were obtained from 2-alkyl phenols and oxazolones via C–H oxidation and cyclization cascade in the presence of silver oxide (Ag₂O) and p-toluenesulfonic acid as a Brønsted acid catalyst. This approach provides a one-pot strategy to synthesize the multisubstituted 3,4-dihydrocoumarins with moderate to high yields (64–81%) and excellent diastereoselectivity (>20:1). Full article

(This article belongs to the Special Issue Application of Cascade/Tandem Reactions in Green Organic Synthesis)

► Show Figures

Graphical abstract

13 pages, 2207 KiB

Open AccessFeature PaperArticle

Rh-Catalyzed Cascade C-H Activation/Annulation of N-Hydroxybenzamides and Propargylic Acetates for Modular Access to Isoquinolones

by Taibei Fang, Shiwen Zhang, Qingqing Ye, Shuwen Kong, Tingting Yang, Kaijie Tang, Xinwei He and Yongjia Shang

Molecules 2022, 27(23), 8553; https://doi.org/10.3390/molecules27238553 - 5 Dec 2022

Cited by 2 | Viewed by 1282

Abstract

A sequential Rh(III)-catalyzed C-H activation/annulation of N-hydroxybenzamides with propargylic acetates leading to the formation of NH-free isoquinolones is described. This reaction proceeds through a sequential C-H activation/alkyne insertion/intramolecular annulation/N-O bond cleavage procedure, affording a broad spectrum of products with diverse substituents in [...] Read more.

A sequential Rh(III)-catalyzed C-H activation/annulation of N-hydroxybenzamides with propargylic acetates leading to the formation of NH-free isoquinolones is described. This reaction proceeds through a sequential C-H activation/alkyne insertion/intramolecular annulation/N-O bond cleavage procedure, affording a broad spectrum of products with diverse substituents in moderate-to-excellent yields. Notably, this protocol features the simultaneous formation of two new C-C/C-N bonds and one heterocycle in one pot with the release of water as the sole byproduct. Full article

(This article belongs to the Special Issue Application of Cascade/Tandem Reactions in Green Organic Synthesis)

► Show Figures

Graphical abstract

Review

Jump to: Research

24 pages, 3709 KiB

Open AccessReview

Recent Advances in the Synthesis of 3,n-Fused Tricyclic Indole Skeletons via Palladium-Catalyzed Domino Reactions

by Liangxin Fan, Xinxin Zhu, Xingyuan Liu, Fangyu He, Guoyu Yang, Cuilian Xu and Xifa Yang

Molecules 2023, 28(4), 1647; https://doi.org/10.3390/molecules28041647 - 8 Feb 2023

Cited by 2 | Viewed by 2290

Abstract

3,n-fused (n = 4–7) tricyclic indoles are pervasive motifs, embedded in a variety of biologically active molecules and natural products. Thus, numerous catalytic methods have been developed for the synthesis of these skeletons over the past few decades. In particular, palladium-catalyzed transformations [...] Read more.

3,n-fused (n = 4–7) tricyclic indoles are pervasive motifs, embedded in a variety of biologically active molecules and natural products. Thus, numerous catalytic methods have been developed for the synthesis of these skeletons over the past few decades. In particular, palladium-catalyzed transformations have received much attention in recent years. This review summarizes recent developments in the synthesis of these tricyclic indoles with palladium-catalyzed domino reactions and their applications in the total synthesis of representative natural products. Full article

(This article belongs to the Special Issue Application of Cascade/Tandem Reactions in Green Organic Synthesis)

► Show Figures